Display device and electronic device

ABSTRACT

A display device whose aspect ratio can be changed is provided. The display device includes a plurality of display units and a plurality of driver circuit units. The plurality of display units each include a light-emitting portion and a connection region. The plurality of driver circuit units each include a driver circuit portion and a connection region. The connection regions of the adjacent units overlap with each other and one shaft passes through the connection regions. The adjacent units are electrically connected to each other with the one shaft. With such a structure, an angle between the adjacent units electrically connected to each other with one shaft can be changed, which enables the aspect ratio of the display device to be changed.

TECHNICAL FIELD

The present invention relates to a display device and an electronicdevice.

Note that one embodiment of the present invention is not limited to theabove technical field. The technical field of the invention disclosed inthis specification and the like relates to an object, a method, or amanufacturing method. In addition, one embodiment of the presentinvention relates to a process, a machine, manufacture, or a compositionof matter. Specifically, examples of the technical field of oneembodiment of the present invention disclosed in this specificationinclude a semiconductor device, a display device, a liquid crystaldisplay device, a light-emitting device, a power storage device, animaging device, a memory device, a processor, an electronic device, asystem, a method for driving any of them, a method for manufacturing anyof them, and a method for testing any of them.

BACKGROUND ART

In recent years, research and development have been extensivelyconducted on light-emitting elements utilizing electroluminescence (EL)used as display elements in a display region of a display device. As abasic structure of these light-emitting elements, a layer containing alight-emitting substance is provided between a pair of electrodes.Voltage is applied to the light-emitting element to obtain lightemission from the light-emitting substance.

The light-emitting element is a self-luminous element; thus, a displaydevice using the light-emitting elements has, in particular, advantagessuch as high visibility, no necessity of a backlight, and low powerconsumption. The display device using the light-emitting elements alsohas advantages in that it can be manufactured to be thin and lightweightand has high response speed.

A display device including the light-emitting elements can haveflexibility; therefore, the use of a flexible substrate for the displaydevice has been considered.

As a method for manufacturing a display device using a flexiblesubstrate, a technique has been developed in which an oxide layer and ametal layer are formed between a substrate and a semiconductor element,the substrate is separated by utilizing weak adhesion of an interfacebetween the oxide layer and the metal layer, and then the semiconductorelement is transferred to another substrate (e.g., a flexible substrate)(Patent Document 1).

In some cases, over a light-emitting element that has been formed over aflexible substrate, another flexible substrate is provided in order toprotect a surface of the light-emitting element or prevent entry ofmoisture or impurities from the outside.

The display device including a flexible substrate can be flexible. Thus,the substrate is preferably formed using a material with low elasticity,high degree of extensibility in stretching, high restorability after thestretch, and the like. Patent Document 2 discloses a structure body forelectronics including a resin composition with high tensile stressrelaxivity and excellent restorability after the stretch.

REFERENCES Patent Document

-   [Patent Document 1] Japanese Published Patent Application No.    2003-174153-   [Patent Document 2] Japanese Published Patent Application No.    2016-102669

DISCLOSURE OF INVENTION

In the case of a display device including a light-emitting element overa flexible substrate, the display device can be stretched in some casesdepending on the material of the substrate. When the display device isstretched, the display device can be made to have a size different froma standard size in some cases.

However, there is a limit on the degree of elasticity of the flexiblesubstrate; thus, excessive stretch might cause damage to the substrate.Even when the substrate is not damaged, a light-emitting element, acircuit element, a wiring, and the like provided over the substratemight be damaged.

Stretching the display device including the flexible substrate mightlead to a decrease in the intensity of light emitted from each unit areaof the display device. This is because the number of pixels per unitarea (also referred to as resolution in some cases) of the stretcheddisplay device decreases. Thus, when the stretched display device isused, the quality of an image displayed on the display device is reducedin some cases.

An object of one embodiment of the present invention is to provide anovel display device that can be changed in shape. Another object of oneembodiment of the present invention is to provide a novel display devicehaving high display quality even with a change in its shape. Anotherobject of one embodiment of the present invention is to provide anelectronic device including the above-described display device.

Note that the descriptions of these objects do not disturb the existenceof other objects. In one embodiment of the present invention, there isno need to achieve all the objects. Other objects will be apparent fromand can be derived from the description of the specification, thedrawings, the claims, and the like.

(1) One embodiment of the present invention is a display device whoseaspect ratio can be changed. The display device includes a displayregion including a first unit and a second unit. The first unit and thesecond unit each include a light-emitting portion and a connectionregion. The connection region of the first unit is electricallyconnected to the connection region of the second unit. The displayregion has a function of changing an angle between the first unit andthe second unit.

(2) Another embodiment of the present invention is the display deviceaccording to (1), including a driver region. The driver region includesa third unit. The third unit includes a driver circuit portion. Thedriver circuit portion has a function of driving the light-emittingportion of the first unit and the light-emitting portion of the secondunit. The third unit of the driver region is parallel to one of thefirst unit and the second unit.

(3) Another embodiment of the present invention is the display deviceaccording to (1) or (2) in which a length in a first direction of thefirst unit is longer than a length in a second direction of the firstunit.

(4) Another embodiment of the present invention is a display devicewhose aspect ratio can be changed. The display device includes a displayregion and a driver region. The display region includes a plurality offirst units. The driver region includes a plurality of second units. Theplurality of first units each include a connection region, and theplurality of second units each include a connection region. Someconnection regions of the plurality of first units are electricallyconnected to some connection regions of the plurality of second units.The plurality of first units of the display region are parallel to eachother. The plurality of second units of the driver region are parallelto each other. An angle between one first unit and one second unit whichis connected to the first unit can be changed.

(5) Another embodiment of the present invention is the display deviceaccording to (4) in which the plurality of first units each include alight-emitting portion. At least one of the plurality of first unitsincludes a driver circuit portion. The plurality of second units eachinclude a driver circuit portion. At least one of the plurality ofsecond units includes a light-emitting portion.

(6) Another embodiment of the present invention is a display devicewhose aspect ratio can be changed. The display device includes a displayregion. The display region includes a first unit and a second unit. Thefirst unit and the second unit each include a light-emitting portion.The second unit overlaps with a first region of the first unit. Thedisplay region has a function of changing an area of the first region.

(7) Another embodiment of the present invention is the display deviceaccording to (6), including a driver region. The driver region includesa third unit and a fourth unit. The third unit has a function of drivingthe light-emitting portion of the first unit. The fourth unit has afunction of driving the light-emitting portion of the second unit. Thefourth unit overlaps with a first region of the third unit. The driverregion has a function of changing an area of the first region of thethird unit.

(8) Another embodiment of the present invention is the display deviceaccording to (7), including a first insulator and a second insulator.The first unit and the third unit are each covered with the firstinsulator. The second unit and the fourth unit are each covered with thesecond insulator. The second insulator is positioned over the firstinsulator. The first insulator and the second insulator have elasticity.

(9) Another embodiment of the present invention is the display deviceaccording to (6), including a third unit and a first insulator. Thethird unit has a function of driving the light-emitting portions of thefirst unit and the second unit. The first unit, the second unit, and thethird unit are each covered with the first insulator. The firstinsulator has elasticity.

(10) Another embodiment of the present invention is the display deviceaccording to any one of (1) to (3) and (5) to (9), in which thelight-emitting portions each include a light-emitting element.

(11) Another embodiment of the present invention is an electronic deviceincluding the display device according to any one of (1) to (10).

According to one embodiment of the present invention, a novel displaydevice that can be changed in shape can be provided. According toanother embodiment of the present invention, a novel display devicehaving high display quality even with a change in its shape can beprovided. According to another embodiment of the present invention, anelectronic device including the above-described display device can beprovided.

Note that the descriptions of these effects do not disturb the existenceof other effects. One embodiment of the present invention does notnecessarily achieve all the effects. Other effects will be apparent fromand can be derived from the description of the specification, thedrawings, the claims, and the like.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIGS. 1A, 1B, 1C, 1D1, and 1D2 illustrate examples of display devices;

FIGS. 2A to 2C illustrate an example of constituting the display devicein FIGS. 1D1 and 1D2;

FIGS. 3A to 3C are a top view and cross-sectional views of part of adisplay device;

FIGS. 4A and 4B are cross-sectional views illustrating an example of ashaft;

FIGS. 5A and 5B are each a perspective view illustrating an example of aconductor included in a shaft;

FIG. 6 is a cross-sectional view illustrating an example of a shaft;

FIGS. 7A and 7B are a perspective view and a cross-sectional viewillustrating an example of a shaft;

FIGS. 8A, 8B, 8C1, 8C2, 8D1, 8D2, and 8E illustrate examples of displaydevices;

FIGS. 9A to 9C illustrate an example of a display device and an exampleof constituting the display device;

FIGS. 10A1, 10A2, 10B1, and 10B2 illustrate examples of electronicdevices;

FIGS. 11A and 11B illustrate examples of electronic devices;

FIGS. 12A, 12B1, and 12B2 are schematic views illustrating examples ofdisplay regions;

FIGS. 13A1 and 13A2 are each a schematic view illustrating an example ofa display region;

FIGS. 14A, 14B1, and 14B2 are schematic views illustrating examples ofdisplay regions;

FIGS. 15A, 15B1, and 15B2 are a schematic view and cross-sectional viewsillustrating examples of display regions;

FIGS. 16A, 16B1, and 16B2 are a schematic view and cross-sectional viewsillustrating examples of display regions;

FIGS. 17A and 17B are schematic views illustrating examples of a displaydevice;

FIGS. 18A, 18B1, and 18B2 are a schematic view and cross-sectional viewsillustrating examples of display devices;

FIGS. 19A to 19C are cross-sectional views illustrating an example of amethod for manufacturing a display device;

FIGS. 20A and 20B are cross-sectional views illustrating an example of amethod for manufacturing a display device;

FIGS. 21A and 21B are cross-sectional views illustrating an example of amethod for manufacturing a display device;

FIG. 22 is a cross-sectional view illustrating an example of a methodfor manufacturing a display device;

FIG. 23 is a cross-sectional view illustrating an example of a methodfor manufacturing a display device;

FIGS. 24A and 24B are cross-sectional views illustrating an example of amethod for manufacturing a display device;

FIGS. 25A to 25D illustrate examples of electronic devices;

FIGS. 26A and 26B illustrate examples of electronic devices;

FIGS. 27A to 27D illustrate structures of light-emitting elements;

FIGS. 28A to 28C illustrate light-emitting devices;

FIG. 29 is a cross-sectional view illustrating an example of a sample;and

FIGS. 30A to 30D are each a photograph of a sample.

BEST MODE FOR CARRYING OUT THE INVENTION

(Notes on the Description in this Specification and the Like)

First, notes on the description of structures in the followingembodiments and example are described.

<Notes on One Embodiment of the Present Invention Described inEmbodiments and Example>

One embodiment of the present invention can be constituted byappropriately combining the structure described in an embodiment withany of the structures described in the other embodiments and Example. Inaddition, in the case where a plurality of structure examples aredescribed in one embodiment, some of the structure examples can becombined as appropriate.

Note that what is described (or part thereof) in an embodiment can beapplied to, combined with, or replaced with another content in the sameembodiment and/or what is described (or part thereof) in anotherembodiment or other embodiments.

Note that in each embodiment and example, a content described in theembodiment and example is a content described with reference to avariety of diagrams or a content described with text in thespecification.

Note that by combining a diagram (or part thereof) described in oneembodiment or one example with another part of the diagram, a differentdiagram (or part thereof) described in the embodiment or example, and/ora diagram (or part thereof) described in another embodiment, otherembodiments, or an example, much more diagrams can be formed.

<Notes on Ordinal Numbers>

In this specification and the like, ordinal numbers such as first,second, and third are used in order to avoid confusion among components.Thus, the terms do not limit the number or order of components. In thisspecification and the like, for example, a “first” component in oneembodiment can be referred to as a “second” component in otherembodiments or claims. Furthermore, in this specification and the like,for example, a “first” component in one embodiment can be omitted inother embodiments or claims.

<Notes on the Description for Drawings>

Embodiments and Example are described with reference to drawings.However, the embodiments and the example can be implemented with variousmodes. It is readily appreciated by those skilled in the art that modesand details can be changed in various ways without departing from thespirit and scope of the present invention. Thus, the present inventionshould not be interpreted as being limited to the description of theembodiments and example. Note that in the structures of the invention inthe embodiments and example, the same portions or portions havingsimilar functions are denoted by the same reference numerals indifferent drawings, and the description of such portions is notrepeated.

In this specification and the like, the terms for explainingarrangement, such as “over” and “under,” are used for convenience todescribe the positional relation between components with reference todrawings. Furthermore, the positional relation between components ischanged as appropriate in accordance with a direction in which thecomponents are described. Therefore, the terms for explainingarrangement are not limited to those used in this specification and maybe changed to other terms as appropriate depending on the situation.

The term “over” or “under” does not necessarily mean that a component isplaced directly over or directly under and directly in contact withanother component. For example, the expression “electrode B overinsulating layer A” does not necessarily mean that the electrode B is onand in direct contact with the insulating layer A and can mean the casewhere another component is provided between the insulating layer A andthe electrode B.

In drawings, the size, the layer thickness, or the region is determinedarbitrarily for description convenience. Therefore, the size, the layerthickness, or the region is not limited to the illustrated scale. Notethat the drawings are schematically shown for clarity, and embodimentsof the present invention are not limited to shapes or values shown inthe drawings. For example, the following can be included: variation insignal, voltage, or current due to noise or difference in timing.

In drawings such as perspective views, some components might not beillustrated for clarity of the drawings.

In the drawings, the same components, components having similarfunctions, components formed of the same material, or components formedat the same time are denoted by the same reference numerals in somecases, and the description thereof is not repeated in some cases.

<Notes on Expressions that can be Rephrased>

In this specification and the like, the terms “one of a source and adrain” (or a first electrode or a first terminal) and “the other of thesource and the drain” (or a second electrode or a second terminal) areused to describe the connection relation of a transistor. This isbecause a source and a drain of a transistor are interchangeabledepending on the structure, operation conditions, or the like of thetransistor. Note that the source or the drain of the transistor can alsobe referred to as a source (or drain) terminal, a source (or drain)electrode, or the like as appropriate depending on the situation. Inthis specification and the like, two terminals except a gate aresometimes referred to as a first terminal and a second terminal or as athird terminal and a fourth terminal. In this specification and thelike, in the case where a transistor has two or more gates (thisstructure is referred to as a multi-gate structure in some cases), thesegates are referred to as a first gate and a second gate in some cases.Note that a “bottom gate” is a terminal that is formed before a channelformation region in manufacture of a transistor, and a “top gate” is aterminal that is formed after a channel formation region in manufactureof a transistor.

In addition, in this specification and the like, the term such as an“electrode” or a “wiring” does not limit a function of the component.For example, an “electrode” is used as part of a “wiring” in some cases,and vice versa. Furthermore, the term “electrode” or “wiring” can alsomean a combination of a plurality of “electrodes” and “wirings” formedin an integrated manner.

In this specification and the like, “voltage” and “potential” can bereplaced with each other. The term “voltage” refers to a potentialdifference from a reference potential. When the reference potential is aground potential, for example, “voltage” can be replaced with“potential”. The ground potential does not necessarily mean 0 V.Potentials are relative values, and the potential applied to a wiring orthe like is changed depending on the reference potential, in some cases.

In this specification and the like, the terms “film” and “layer” can beinterchanged with each other depending on the case or circumstances. Forexample, the term “conductive layer” can be changed into the term“conductive film” in some cases. Moreover, the term “insulating film”can be changed into the term “insulating layer” in some cases, or can bereplaced with a word not including the term “film” or “layer” dependingon the case or circumstances. For example, the term “conductive layer”or “conductive film” can be changed into the term “conductor” in somecases. Furthermore, for example, the term “insulating layer” or“insulating film” can be changed into the term “insulator” in somecases.

In this specification and the like, the terms “wiring”, “signal line”,“power supply line”, and the like can be interchanged with each otherdepending on circumstances or conditions. For example, the term “wiring”can be changed into the term such as “signal line” or “power supplyline” in some cases. The term such as “signal line” or “power supplyline” can be changed into the term “wiring” in some cases. The term suchas “power supply line” can be changed into the term such as “signalline” in some cases. The term such as “signal line” can be changed intothe term such as “power supply line” in some cases. The term “potential”that is applied to a wiring can be changed into the term “signal” or thelike depending on circumstances or conditions. Inversely, the term“signal” or the like can be changed into the term “potential” in somecases.

<Notes on Definitions of Terms>

Definitions of the terms that will be mentioned in the followingembodiments and example are described below.

<<Impurity in Semiconductor>>

An impurity in a semiconductor refers to, for example, elements otherthan the main components of a semiconductor layer. For example, anelement with a concentration of lower than 0.1 atomic % is an impurity.When an impurity is contained, the density of states (DOS) may be formedin a semiconductor, the carrier mobility may be decreased, or thecrystallinity may be decreased. In the case where the semiconductor isan oxide semiconductor, examples of an impurity that changescharacteristics of the semiconductor include Group 1 elements, Group 2elements, Group 13 elements, Group 14 elements, Group 15 elements, andtransition metals other than the main components of the semiconductor;specifically, there are hydrogen (included in water), lithium, sodium,silicon, boron, phosphorus, carbon, and nitrogen, for example. When thesemiconductor is an oxide semiconductor, oxygen vacancies may be formedby entry of impurities such as hydrogen, for example. Furthermore, whenthe semiconductor is a silicon layer, examples of an impurity thatchanges the characteristics of the semiconductor include oxygen, Group 1elements except hydrogen, Group 2 elements, Group 13 elements, and Group15 elements.

<<Transistor>>

In this specification, a transistor is an element having at least threeterminals of a gate, a drain, and a source. The transistor has a channelformation region between the drain (a drain terminal, a drain region, ora drain electrode) and the source (a source terminal, a source region,or a source electrode). Voltage is applied between the gate and thesource, whereby current can flow between the source and the drain.

Furthermore, functions of a source and a drain might be switched when atransistor of opposite polarity is employed or a direction of currentflow is changed in circuit operation, for example. Therefore, the terms“source” and “drain” can be switched in this specification and the like.

<<Switch>>

In this specification and the like, a switch is conducting (on state) ornot conducting (off state) to determine whether current flowstherethrough or not. Alternatively, a switch has a function of selectingand changing a current path.

Examples of a switch include an electrical switch and a mechanicalswitch. That is, any element can be used as a switch as long as it cancontrol current, without limitation to a certain element.

Examples of the electrical switch include a transistor (e.g., a bipolartransistor or a MOS transistor), a diode (e.g., a PN diode, a PIN diode,a Schottky diode, a metal-insulator-metal (MIM) diode, ametal-insulator-semiconductor (MIS) diode, or a diode-connectedtransistor), and a logic circuit in which such elements are combined.

In the case of using a transistor as a switch, an “on state” of thetransistor refers to a state in which a source electrode and a drainelectrode of the transistor are electrically short-circuited.Furthermore, an “off state” of the transistor refers to a state in whichthe source electrode and the drain electrode of the transistor areelectrically cut off. In the case where a transistor operates just as aswitch, the polarity (conductivity type) of the transistor is notparticularly limited to a certain type.

An example of a mechanical switch is a switch formed using a microelectro mechanical systems (MEMS) technology, such as a digitalmicromirror device (DMD). Such a switch includes an electrode that canbe moved mechanically, and operates by controlling conduction andnon-conduction in accordance with movement of the electrode.

<<Connection>>

In this specification and the like, when it is described that X and Yare connected, the case where X and Y are electrically connected, thecase where X and Y are functionally connected, and the case where X andY are directly connected are included therein. Accordingly, withoutbeing limited to a predetermined connection relation, for example, aconnection relation other than that shown in a drawing or text is alsopossible.

Here, X, Y, and the like each denote an object (e.g., a device, anelement, a circuit, a wiring, an electrode, a terminal, a conductivefilm, or a layer).

For example, in the case where X and Y are electrically connected, oneor more elements that enable an electrical connection between X and Y(e.g., a switch, a transistor, a capacitor, an inductor, a resistor, adiode, a display element, a light-emitting element, or a load) can beconnected between X and Y. Note that the switch is controlled to beturned on or off. That is, a switch is conducting or not conducting (isturned on or off) to determine whether current flows therethrough ornot.

For example, in the case where X and Y are functionally connected, oneor more circuits that enable functional connection between X and Y(e.g., a logic circuit such as an inverter, a NAND circuit, or a NORcircuit; a signal converter circuit such as a DA converter circuit, anAD converter circuit, or a gamma correction circuit; a potential levelconverter circuit such as a power source circuit (e.g., a step-upconverter or a step-down converter) or a level shifter circuit forchanging the potential level of a signal; a voltage source; a currentsource; a switching circuit; an amplifier circuit such as a circuit thatcan increase signal amplitude, the amount of current, or the like, anoperational amplifier, a differential amplifier circuit, a sourcefollower circuit, or a buffer circuit; a signal generation circuit; amemory circuit; and/or a control circuit) can be connected between X andY. For example, even when another circuit is interposed between X and Y,X and Y are functionally connected when a signal output from X istransmitted to Y.

Note that when it is explicitly described that X and Y are electricallyconnected, the case where X and Y are electrically connected (i.e., thecase where X and Y are connected with another element or another circuitprovided therebetween), the case where X and Y are functionallyconnected (i.e., the case where X and Y are functionally connected withanother circuit provided therebetween), and the case where X and Y aredirectly connected (i.e., the case where X and Y are connected withoutanother element or another circuit provided therebetween) are includedtherein. That is, the explicit expression “X and Y are electricallyconnected” is the same as the explicit simple expression “X and Y areconnected”.

For example, any of the following expressions can be used for the casewhere a source (or a first terminal or the like) of a transistor iselectrically connected to X through (or not through) Z1 and a drain (ora second terminal or the like) of the transistor is electricallyconnected to Y through (or not through) Z2, or the case where a source(or a first terminal or the like) of a transistor is directly connectedto one part of Z1 and another part of Z1 is directly connected to Xwhile a drain (or a second terminal or the like) of the transistor isdirectly connected to one part of Z2 and another part of Z2 is directlyconnected to Y.

The expressions include, for example, “X, Y, a source (or a firstterminal or the like) of a transistor, and a drain (or a second terminalor the like) of the transistor are electrically connected to each other,and X, the source (or the first terminal or the like) of the transistor,the drain (or the second terminal or the like) of the transistor, and Yare electrically connected to each other in this order”, “a source (or afirst terminal or the like) of a transistor is electrically connected toX, a drain (or a second terminal or the like) of the transistor iselectrically connected to Y, and X, the source (or the first terminal orthe like) of the transistor, the drain (or the second terminal or thelike) of the transistor, and Y are electrically connected to each otherin this order”, and “X is electrically connected to Y through a source(or a first terminal or the like) and a drain (or a second terminal orthe like) of a transistor, and X, the source (or the first terminal orthe like) of the transistor, the drain (or the second terminal or thelike) of the transistor, and Y are provided to be connected in thisorder”. When the connection order in a circuit configuration is definedby an expression similar to the above examples, a source (or a firstterminal or the like) and a drain (or a second terminal or the like) ofa transistor can be distinguished from each other to specify thetechnical scope. Note that these expressions are examples and there isno limitation on the expressions. Here, X, Y, Z1, and Z2 each denote anobject (e.g., a device, an element, a circuit, a wiring, an electrode, aterminal, a conductive film, or a layer).

Even when independent components are electrically connected to eachother in a circuit diagram, one component has functions of a pluralityof components in some cases. For example, when part of a wiring alsofunctions as an electrode, one conductive film functions as the wiringand the electrode. Thus, “electrical connection” in this specificationincludes in its category such a case where one conductive film hasfunctions of a plurality of components.

<<Parallel and Perpendicular>>

In this specification, the term “parallel” indicates that the angleformed between two straight lines is greater than or equal to −10° andless than or equal to 10°, and accordingly also includes the case wherethe angle is greater than or equal to −5° and less than or equal to 5°.The term “substantially parallel” indicates that the angle formedbetween two straight lines is greater than or equal to −30° and lessthan or equal to 30°. The term “perpendicular” indicates that the angleformed between two straight lines is greater than or equal to 80° andless than or equal to 100°, and accordingly also includes the case wherethe angle is greater than or equal to 85° and less than or equal to 95°.The term “substantially perpendicular” indicates that the angle formedbetween two straight lines is greater than or equal to 60° and less thanor equal to 120°.

Embodiment 1

In this embodiment, a display device disclosed in one embodiment of thepresent invention is described.

<Structure Example>

FIGS. 1A, 1B, and 1C illustrate a display unit, a driver circuit unit,and a support unit, respectively, that are included in the displaydevice of one embodiment of the present invention. A display unit 80illustrated in FIG. 1A includes a light-emitting portion 81, aconnection region 82, and a support 83. A driver circuit unit 90illustrated in FIG. 1B includes a driver circuit portion 91, aconnection region 92, and a support 93. A support unit 70 illustrated inFIG. 1C includes a connection region 72 and a support 73.

The light-emitting portion 81 of the display unit 80 includes alight-emitting element and a pixel circuit. Examples of thelight-emitting element include a transmissive liquid crystal element, anorganic EL element, an inorganic EL element, and a nitride semiconductorlight-emitting diode. Instead of the light-emitting element, areflective liquid crystal element, an electrophoretic element, or thelike can be used. The pixel circuit is a circuit for making thelight-emitting element emit light. A terminal electrically connected tothe circuit is included in the connection region 82.

Note that the light-emitting portion 81 may be a pixel including aplurality of light-emitting elements. For example, the plurality oflight-emitting elements may emit light of three colors of red (R), green(G), and blue (B), or four colors of red (R), green (G), blue (B), andwhite (W). Alternatively, the plurality of light-emitting elements mayemit light of some of red (R), green (G), blue (B), white (W), cyan (C),yellow (Y), magenta (M), and the like in combination as necessary. Thelight-emitting portion 81 of the display unit 80 is not necessarily thepixel including the plurality of light-emitting elements, and may be asubpixel including a light-emitting element emitting light of any one ofthe above colors, for example.

The driver circuit portion 91 of the driver circuit unit 90 has afunction of driving the pixel circuit included in the display unit 80 tomake the light-emitting element emit light. For the driver circuitportion 91, a source driver circuit, a gate driver circuit, or the likecan be used. A terminal electrically connected to the driver circuitportion 91 is included in the connection region 92.

The connection regions 72, 82, and 92 are provided so that each unit canbe electrically connected to other units. Note that a method forconnecting the units to each other is described later.

FIG. 1D1 illustrates the display device of one embodiment of the presentinvention. A display device 100 is functionally divided into a displayregion 101, a driver region 102A, and a driver region 102B.

The display region 101 includes a plurality of display units 80. Thedriver region 102A includes a plurality of driver circuit units 90. Thedriver region 102B includes a plurality of driver circuit units 90 thatare different from those in the driver region 102A. The display device100 also includes the support unit 70. In FIGS. 1D1 and 1D2, the supportunit 70 is not included in the display region 101, the driver region102A, nor the driver region 102B.

The units are connected to each other with a shaft 60 passing throughthe connection regions of the units. Thus, the units include openingsfor the shaft 60 in the connection regions. For example, in a region 105a, one shaft 60 passes through the connection regions 82 of four displayunits 80, whereby the four display units 80 are connected to oneanother. For another example, in a region 105 b, one shaft 60 passesthrough the connection regions 82 of two display units 80 and theconnection regions 92 of two driver circuit units 90, whereby the twodisplay units 80 and the two driver circuit units 90 are connected toone another. Note that the shaft 60 is a structure body for electricallyconnecting the units to each other; the details of the shaft 60 aredescribed later.

As described above, for the driver circuit portion 91 included in thedriver circuit unit 90, a source driver circuit, a gate driver circuit,or the like can be used. Thus, the plurality of driver circuit units 90included in the driver region 102A can constitute one of the sourcedriver circuit and the gate driver circuit by being electricallyconnected to each other with the shaft 60. In addition, the plurality ofdriver circuit units 90 included in the driver region 102B canconstitute the other of the source driver circuit and the gate drivercircuit by being electrically connected to each other with the shaft 60.

The support unit 70 has a function of maintaining the structure of thedisplay device 100. In FIG. 1D1, one of the connection regions 72 of thesupport unit 70 is connected to the connection region 92 of the drivercircuit unit 90 in the driver region 102A with the shaft 60, and theother of the connection regions 72 of the support unit 70 is connectedto the connection region 92 of the driver circuit unit 90 in the driverregion 102B with the shaft 60. Note that the support unit 70 may beprovided with a wiring, a circuit, an element, or the like. In thatcase, the connection region 72 of the support unit 70 is electricallyconnected to the connection region 92 of the driver circuit unit 90 withthe shaft 60. In the case where the display device 100 does not need thesupport unit 70, the support unit 70 may be omitted from the componentsof the display device 100.

Note that the display unit, the driver circuit unit, and the supportunit are each rotatable on the shaft 60 in the connection region. Forexample, although an angle θ between the dotted line X1-X2 and thedotted line X1-X3 is 45° in the display device 100 in FIG. 1D1, theunits may be rotated until the angle θ becomes 30° to change the shapeof the display device 100 as illustrated in FIG. 1D2. In that case, thedisplay device 100 in FIG. 1D1 is stretched by approximately 1.2 timesin the x direction and approximately 0.71 times in the y direction tohave the shape in FIG. 1D2. That is, by changing the angle θ, the aspectratio of the display device 100 can be changed. In the case where thedisplay device 100 is stretched as much as possible, the display device100 is configured so that the units are movable in the range of theangle θ of approximately 10° to 80°. Depending on the shape of thedisplay unit 80, the range of the angle θ becomes narrower than or widerthan the above-described range of 10° to 80°.

Note that because of the structure of the display device 100, some ofthe plurality of driver circuit units 90 included in the driver region102A and the driver region 102B are parallel to some of the displayunits 80 included in the display region 101.

As described above, the display device 100 in FIG. 1D1 that is formedusing the plurality of display units 80, the plurality of driver circuitunits 90, and the support unit 70 can be a stretchable display device.

<Configuration Method>

Next, a method for connecting the units to each other to form thedisplay device 100 in FIG. 1D1 is described.

FIGS. 2A to 2C illustrate an example of the method for connecting theunits to each other. Only the display unit 80 is described in thisexample; however, depending on circumstances or conditions or as needed,the display unit may be replaced with the driver circuit unit or thesupport unit.

[Step 1]

FIG. 2A illustrates a display unit group 85 combining four display units80 (display units 80 a, 80 b, 80 c, and 80 d). The display unit 80 aincludes a region where one of the two connection regions 82 of thedisplay unit 80 a overlaps with one of the two connection regions 82 ofthe display unit 80 b, and a region where the other of the twoconnection regions 82 of the display unit 80 a overlaps with one of thetwo connection regions 82 of the display unit 80 c. The display unit 80d includes a region where one of the two connection regions 82 of thedisplay unit 80 d overlaps with the other of the two connection regions82 of the display unit 80 b, and a region where the other of the twoconnection regions 82 of the display unit 80 d overlaps with the otherof the two connection regions 82 of the display unit 80 c. Note that inthe display unit group 85 in FIGS. 2A to 2C, the display unit 80 a andthe display unit 80 d are provided on the lower side, and the displayunit 80 b and the display unit 80 c are provided on the upper side.

[Step 2]

Next, four display unit groups 85 are provided so that the connectionregions 82 of the four display unit groups 85 overlap with theconnection regions 82 of the display unit group 85 in FIG. 2A (see FIG.2B). Then, the shafts 60 are provided in the overlapping connectionregions 82 to connect four display units to each other. In order toavoid complexity of description, the display unit group 85 in FIG. 2A isindicated by a different hatching pattern from the other display unitgroups 85 in FIG. 2B.

[Step 3]

After that, another four display unit groups 85 are provided underconnection regions 82 a, 82 b, 82 c, 82 d, 82 e, 82 f, 82 g, and 82 h inFIG. 2B and electrically connected to the connection regions with theshafts 60. Specifically, one of the four display unit groups 85 isprovided under the connection regions 82 a and 82 b and electricallyconnected thereto with shafts 60 a and 60 b; one of the remaining threedisplay unit groups 85 is provided under the connection regions 82 c and82 d and electrically connected thereto with shafts 60 c and 60 d; oneof the remaining two display unit groups 85 is provided under theconnection regions 82 e and 82 f and electrically connected thereto withshafts 60 e and 60 f; and the remaining display unit group 85 isprovided under the connection regions 82 g and 82 h and electricallyconnected thereto with shafts 60 g and 60 h (see FIG. 2C). Note that inorder to avoid complexity of description, in FIG. 2C, the display unitgroup 85 in FIG. 2A and the display unit groups 85 newly electricallyconnected to the connection regions in Step 3 are indicated by differenthatching patterns from the other display unit groups 85. That is, inFIG. 2C, the hatching patterns of the display unit groups 85 on theupper side are not changed, whereas the hatching patterns of the displayunit groups 85 on the lower side are changed.

As described above, the display device can be configured by connectingthe adjacent display unit groups 85 to each other so that one of them ispositioned on the upper side and the other is positioned on the lowerside.

Note that in the case where no display unit groups 85 are providedadjacent to the display unit groups 85 (e.g., when no display unitgroups 85 are newly provided in a region 106 in FIG. 2C), the displayunits are electrically connected to each other with shafts 61 passingthrough the connection regions 82 in the region 106. For anotherexample, when no display unit groups 85 are provided adjacent to thedisplay unit groups 85 in a region other than the region 106, thedisplay units are electrically connected to each other with the shafts61 passing through the connection regions in the region.

Next, a cross section of the display device formed by theabove-described method is described.

FIG. 3A illustrates a region 101 a in FIG. 2C. FIG. 3B is across-sectional view taken along the dashed-dotted line A1-A2 in FIG.3A, and FIG. 3C is a cross-sectional view taken along the dashed-twodotted line B1-B2 in FIG. 3A. The shafts 60 e to 60 h, a shaft 60 i, andthe shafts 61 that have a function of connecting the display units 80 toeach other are also illustrated in FIGS. 3B and 3C.

In the region 101 a, display unit groups 85A, 85B, and 85C areelectrically connected to each other so that the display unit group 85Bis positioned on the upper side and the display unit groups 85A and 85Care positioned on the lower side. As illustrated in FIGS. 3B and 3C, thedisplay unit group 85B is positioned above the display unit groups 85Aand 85C.

Next, the shafts 60 e to 60 i (collectively referred to as the shaft 60)and a method for electrically connecting the shaft 60 to the displayunits 80 are described. Here, a region 101 b and the shaft 60 h in FIG.3B are described in detail, for example. In the following detaileddescription, the shaft 60 h can be replaced by the shaft 60 e, 60 f, 60g, or 60 i, for example. For the shafts 61, refer to the followingdescription of the shaft 60 h.

FIG. 4A illustrates the details of the region 101 b. FIG. 4B is across-sectional view of the shaft 60 h taken along the dashed-dottedline C1-C2 in FIG. 4A.

The display unit group 85B includes a display unit 80[1] and a displayunit 80[2]. The display unit group 85C includes a display unit 80[3] anda display unit 80[4]. In FIG. 4A, the display unit 80[1] includeswirings 86 b, and the display unit 80[4] includes wirings 86 c. Thewirings 86 b are electrically connected to respective conductors 41 to44. The wirings 86 c are electrically connected to the respectiveconductors 41 to 44.

The shaft 60 h includes the conductors 41 to 44 and conductors 45 to 48.

In the cross-sectional view in FIG. 4B, the conductor 41 is positionedin the center of the shaft 60 h. The conductors 42 to 48 are positionedconcentrically around the conductor 41 (the center of the shaft 60 h).

The conductor 41 has a structure illustrated in a perspective view inFIG. 5A. The conductor 41 includes a disk 41 a, a column 41 b, and adisk 41 c. The column 41 b is provided on the center portions of thedisks 41 a and 41 c. One of the wirings 86 b is electrically connectedto the conductor 41 by contact with a side surface of the disk 41 a. Oneof the wirings 86 c is electrically connected to the conductor 41 bycontact with a side surface of the disk 41 c.

The conductor 44 has a structure illustrated in a perspective view inFIG. 5B. The conductor 44 includes a disk 44 a having a circular hole, ahollow cylinder 44 b, and a disk 44 c having a circular hole. Thecircular hole of the disk 44 a, the circular hole of the disk 44 c, andthe hollow of the cylinder 44 b have the same size. The disk 44 c isprovided on the bottom base of the cylinder 44 b so that the circularhole of the disk 44 c is aligned with the hollow of the cylinder 44 b.The disk 44 a is provided on the upper base of the cylinder 44 b so thatthe circular hole of the disk 44 a is aligned with the hollow of thecylinder 44 b. One of the wirings 86 b is electrically connected to theconductor 44 by contact with a side surface of the disk 44 a. One of thewirings 86 c is electrically connected to the conductor 44 by contactwith a side surface of the disk 44 c.

For the structures of the conductors 42, 43, and 45 to 48, refer to thedescription of the conductor 44.

In FIG. 4A, the conductor 42 has a function of electrically connectingone of the wirings 86 b to one of the wirings 86 c. The conductor 43 hasa function of electrically connecting another one of the wirings 86 b toanother one of the wirings 86 c. Although not illustrated, theconductors 45 to 48 have functions of electrically connecting wiringsincluded in the display unit 80[2] to wirings included in the displayunit 80[3].

When the conductors included in the shaft 60 have the structuresillustrated in FIGS. 4A and 4B and FIGS. 5A and 5B, the units can beelectrically connected to each other with the shaft 60.

FIGS. 4A and 4B illustrate one example of the structure of the shaft 60h, and one embodiment of the present invention is not limited to thisexample. For example, the shaft 60 h may have a structure in FIG. 6instead of the structure in FIGS. 4A and 4B. In the structureillustrated in FIG. 6 , the wirings 86 b are in contact with therespective conductors 41 to 44, and the wirings 86 c are in contact withthe respective conductors 41 to 44. Similarly, the wirings included inthe display unit 80[2] are in contact with the respective conductors 45to 48, and the wirings included in the display unit 80[3] are in contactwith the respective conductors 45 to 48 (the contacts between thewirings and the conductors 45 to 48 are not illustrated in FIG. 6 ).Note that the conductors are positioned on the wirings at the upper sideof the shaft 60 h and the wirings are positioned on the conductors atthe lower side of the shaft 60 h. This structure can reduce the contactresistance between the wirings included in the display units and theconductors included in the shaft 60 h.

Alternatively, the shaft 60 h may include, for example, codes formed ofa ductile and malleable conductor covered with an insulator such asrubber, instead of the conductors 41 to 48. The shaft having such astructure is illustrated in FIGS. 7A and 7B as a shaft 60A. FIG. 7A is aperspective view of the shaft 60A including the codes in place of theconductors 41 to 48. FIG. 7B is a cross-sectional view of the shaft 60Ataken along the planes Y1-Y2 in FIG. 7A.

In FIG. 7A, the shaft 60A includes openings 69 b[1], 69 b[2], 69 c[1],and 69 c[2] for connecting the codes to the wirings (e.g., the wirings86 b and 86 c) included in the display units. Note that the movablerange of the display units depends on the lengths of the openings in thecircumferential direction; the longer the lengths of the openings in thecircumferential direction are, the wider the movable range of thedisplay units is.

FIG. 7B illustrates a structure example of the region 101 b includingthe shaft 60A in FIG. 7A. The shaft 60A includes codes 51 to 54. Thecodes 51 to 54 are used in place of the conductors 41 to 44 in FIGS. 4Aand 4B and FIG. 6 . That is, the codes 51 to 54 have functions ofelectrically connecting the wirings 86 b to the wirings 86 c through theopenings 69 b[1] and 69 c[2]. The codes 51 to 54 have ductility andmalleability to be highly resistant to bending and thus can withstandthe movement of the units connected to each other.

The above-described connection method makes it possible to obtain thedisplay device 100 in FIG. 1D1.

<Modification Example>

One embodiment of the present invention is not limited to the displaydevice 100 in FIG. 1D1. Depending on the circumstances or conditions oras needed, the components of the display device 100 can be changed asappropriate.

For example, instead of the display unit 80 in FIG. 1A, a display unit80A in FIG. 8A whose light-emitting portion is larger than thelight-emitting portion 81 of the display unit 80 may be used. Thedisplay unit 80A includes a light-emitting portion 81A, the connectionregion 82, and a support 83A. The light-emitting portion 81A of thedisplay unit 80A has a larger light-emitting area than thelight-emitting portion 81 of the display unit 80. With an increase inthe light-emitting area of the light-emitting portion 81A, the area ofthe support 83A is increased in the display unit 80A.

FIG. 8B illustrates a display device 100A including the display unit 80Ain place of the display unit 80 of the display device 100 illustrated inFIG. 1D1. The use of the display unit 80A enables the display device100A to have a larger light-emitting area. Thus, the display device 100Acan have a smaller non-display region (a region other than thelight-emitting portion 81) than the display device 100, resulting in anincrease in the emission luminance of the display device 100A.

Here, the case where the size of the support 83A of the display unit 80Ais increased as much as possible is described. FIG. 8C1, FIG. 8D1, andFIG. 8E illustrate a display unit group 86 combining four display units80, a display unit group 86A combining four display units 80A, and adisplay unit group 86B combining four display units 80B, respectively.In the display unit group 86B, the display units 80B have such largesupports that the opposite display units 80B are in contact with eachother.

In this specification and the like, as an index of the size of thedisplay unit, the distance between the center of the shaft in one of theconnection regions and the center of the shaft in the other of theconnection regions in the display unit is defined as a length in a firstdirection. In addition, the width of the display unit in the directionperpendicular to the first direction of the display unit is defined as alength in a second direction.

The distance between the two connection regions of each of the displayunit 80 in FIG. 8C1, the display unit 80A in FIG. 8D1, and the displayunit 80B in FIG. 8E (hereinafter, referred to as the length in the firstdirection) is referred to as L. The lengths in the second direction ofthe display unit 80 in FIG. 8C1, the display unit 80A in FIG. 8D1, andthe display unit 80B in FIG. 8E are referred to as W₁, W₂, and W₃,respectively. Note that W₂ is longer than W₁, and W₃ is longer than W₂.The size of the support of the display unit 80B is as large as possible;thus, W₃ is the maximum value in the display unit group 86B composed ofthe display units 80B.

The opposite display units 80B are in contact with each other in thedisplay unit group 86B in FIG. 8E; thus, the length L in the firstdirection of the display unit 80B is the same as the length W₃ in thesecond direction of the display unit 80B.

In the display unit 80 in FIG. 8C1, the center of the shaft in one ofthe connection regions is referred to as Z1, and the center of the shaftin the other of the connection regions is referred to as Z3. In thedisplay unit group 86 in FIG. 8C1, the center of the shaft in theconnection region that is diagonally opposite to Z1 is referred to asZ2. Similarly, in the display unit 80A in FIG. 8D1, the center of theshaft in one of the connection regions is referred to as Z1, and thecenter of the shaft in the other of the connection regions is referredto as Z3. In the display unit group 86A in FIG. 8D1, the center of theshaft in the connection region that is diagonally opposite to Z1 isreferred to as Z2. Similarly, in the display unit 80B in FIG. 8E, thecenter of the shaft in one of the connection regions is referred to asZ1, and the center of the shaft in the other of the connection regionsis referred to as Z3. In the display unit group 86B in FIG. 8E, thecenter of the shaft in the connection region that is diagonally oppositeto Z1 is referred to as Z2. In each of FIGS. 8C1, 8D1, and 8E, an anglebetween the dotted line Z1-Z2 and the dotted line Z1-Z3 is referred toas B.

The display unit group 86 in FIG. 8C1 is changed in shape such that θhas the minimum value, so that the display unit group 86 has a shape inFIG. 8C2. An angle between the dotted line Z1-Z3 and the dotted lineZ1-Z2 at this time is referred to as ϕ₁. The display unit group 86A inFIG. 8D1 is changed in shape such that θ has the minimum value, so thatthe display unit group 86A has a shape in FIG. 8D2. An angle between thedotted line Z1-Z3 and the dotted line Z1-Z2 at this time is referred toas ϕ₂. Note that the angle ϕ₁ is smaller than the angle ϕ₂.

Note that in FIGS. 8C2 and 8D2, the dotted line Z1-Z3 and the dottedline Z1-Z2 are extended to clearly show the angle ϕ₁ and the angle ϕ₂.

When the second direction length W₁ of the display unit 80 in thedisplay unit group 86 is increased, the shape of the display unit group86 becomes close to that of the display unit group 86A. That is, theincreased second direction length of the display unit increases theminimum value in the range of the angle θ. For the same reason, theincreased second direction length of the display unit reduces themaximum value in the range of the angle θ. In other words, the increasedsecond direction length of the display unit narrows the range of theangle θ in the display unit group including the display unit.

The display unit group 86B in FIG. 8E cannot be changed in shape byreducing the angle θ because the opposite display units 80B are incontact with each other.

Accordingly, in the case where the display device 100A is formed usingthe display unit whose light-emitting portion and support are largerthan the light-emitting portion 81 and the support 83 of the displayunit 80, the length in the second direction of the display unit needs tobe shorter than the length in the first direction of the display unit.

A plurality of units in FIGS. 9A and 9B may be used instead of the unitsin FIGS. 1A to 1C, for example.

A region 100 a in FIG. 9A includes one support unit 70 and a pluralityof units 30. Note that not all the units 30 have the same length andsome of the units 30 have different lengths from the others, and thesupport unit 70 and each of the plurality of units 30 are parallel toeach other. Each of the units 30 includes the light-emitting portion 81and a connection region 32. Some of the units 30 include one or twodriver circuit portions 91, and the others do not include the drivercircuit portion 91.

A region 100 b in FIG. 9B includes a plurality of units 31. Note thatnot all the units 31 have the same length and some of the units 31 havedifferent lengths from the others, and the plurality of units 31 areparallel to each other. Each of the units 31 includes the driver circuitportion 91 and the connection region 32. Some of the units 31 includethe light-emitting portion 81, and the others do not include thelight-emitting portion 81.

A display device 100B in FIG. 9C can be obtained in such a manner thatthe connection regions 32 of the units 31 in FIG. 9B are provided tooverlap with the connection regions 32 of the support unit 70 and theunits 30 in FIG. 9A, and the connection regions 32 are connected to eachother with shafts 62. Such a structure enables the display device 100Bto change its shape so as to be the display device 100 in FIG. 1D2 (thischange is not illustrated), as in the display device 100 in FIG. 1D1.Although the display device 100 in FIG. 1D1 includes four unitsoverlapping with one another as in FIGS. 3B and 3C, the display device100B includes two units overlapping with each other and thus can bestored in a thin housing or the like.

In the above description, the support unit 70 is described as acomponent of the display device 100B; however, the display device 100Bdoes not necessarily include the support unit 70.

Note that this embodiment can be combined with other embodiments and/oran example in this specification as appropriate.

Embodiment 2

In this embodiment, examples of electronic devices each including thedisplay device 100 in Embodiment 1 are described.

Application Example 1

FIGS. 10A1 and 10A2 each illustrate a signboard 6002 provided on theroof of a building 6001. The signboard 6002 is supported by steel frames6003 provided on the roof of the building 6001.

Here, the case where the signboard 6002 includes the display device 100in Embodiment 1 is described. The signboard 6002 in FIG. 10A1 thatincludes the display device 100 can change its shape so as to be asignboard 6002A in FIG. 10A2. Accordingly, the aspect ratio of thesignboard can be freely changed depending on the contents displayed onthe signboard.

Application Example 2

FIGS. 10B1 and 10B2 each illustrate an example of a small-sized digitalsignage that can be easily transferred. A digital signage 6100 in FIG.10B1 includes a display portion 6101, a structure body 6102, and casters6103. The structure body 6102 has a structure supporting the displayportion 6101 and a structure provided with the casters 6103. The digitalsignage 6100 can be transferred by rolling the casters 6103.

Here, the case where the display portion 6101 includes the displaydevice 100 in Embodiment 1 is described. The display portion 6101 inFIG. 10B1 that includes the display device 100 can change its shape soas to be a display portion 6101A in FIG. 10B2. Accordingly, the aspectratio of the display portion can be freely changed depending on thecontents displayed on the display portion.

Application Example 3

FIGS. 11A and 11B each illustrate an example of a digital signage thatcan be attached to a wall. FIG. 11A illustrates a digital signage 6200Aattached to a wall 6201.

Here, the case where the digital signage 6200A includes the displaydevice 100 in Embodiment 1 is described. The digital signage 6200A inFIG. 11A that includes the display device 100 can change its shape so asto be a digital signage 6200B in FIG. 11B. Accordingly, the aspect ratioof the digital signage can be freely changed depending on the contentsdisplayed on the digital signage.

Note that this embodiment can be combined with other embodiments and/oran example in this specification as appropriate.

Embodiment 3

In this embodiment, a display device of one embodiment of the presentinvention that is different from the display device 100 in Embodiment 1is described.

<Structure Example>

FIG. 12A illustrates a structure example of a display unit included inthe display device of one embodiment of the present invention. A displayunit 250 includes a circuit 251, and the circuit 251 includes alight-emitting portion 252.

The circuit 251 is a circuit for making the light-emitting portion 252emit light. A selection signal, a data signal, or the like input to thecircuit 251 through a wiring (not illustrated in FIG. 12A) enables thelight-emitting portion 252 to emit light.

For the light-emitting portion 252, a transmissive liquid crystalelement, an organic EL element, an inorganic EL element, a nitridesemiconductor light-emitting diode, or the like can be used. Instead ofthe light-emitting portion 252, a reflective liquid crystal element, anelectrophoretic element, or the like can be used.

The light-emitting portion 252 may include a plurality of kinds oflight-emitting elements. For example, the plurality of light-emittingelements may emit light of three colors of red (R), green (G), and blue(B), or four colors of red (R), green (G), blue (B), and white (W).Alternatively, the plurality of light-emitting elements may emit lightof some of red (R), green (G), blue (B), white (W), cyan (C), yellow(Y), magenta (M), and the like in combination as necessary. Thelight-emitting portion 252 of the display unit 250 does not necessarilyinclude the plurality of kinds of light-emitting elements, and mayinclude one kind of light-emitting element. For example, thelight-emitting portion may emit light of any one of the above colors.

The display unit 250 in FIGS. 12A, 12B1, and 12B2 may be replaced with apixel. In the case where the pixel is used instead of the display unit250 in this embodiment, the display unit 250, the circuit 251, and thelight-emitting portion 252 may be replaced with a pixel, a pixelcircuit, and a light-emitting element, respectively.

Note that although the display unit 250 in FIGS. 12A, 12B1, and 12B2 hasa square shape, one embodiment of the present invention is not limitedthereto. For example, the display unit 250 may have a circular shape, anelliptical shape, a shape with a curve, a polygonal shape, or the like.In addition, the light-emitting portion 252 does not necessarily have asquare shape, but may have a circular shape, an elliptical shape, ashape with a curve, a polygonal shape, or the like.

FIG. 12B1 illustrates a structure example of a display region in thedisplay device of one embodiment of the present invention. A displayregion 260A has a stacked structure of two layers each including aplurality of display units 250. In FIG. 12B1, the plurality of displayunits 250 in an upper layer of the two layers are referred to as displayunits 250 a, and the plurality of display units 250 in a lower layer ofthe two layers are referred to as display units 250 b. To avoidcomplexity of description, wirings connected to the display units 250 aand the display units 250 b are not illustrated in FIG. 12B1.

Note that the display region 260A includes an elastic andlight-transmitting insulator 240. In this specification and the like, anelastic material refers to a material that can expand and contract andhas high restorability. In addition, a light-transmitting materialrefers to a material with high transmittance. The insulator 240 has atwo-layer structure of the upper layer and the lower layer. The upperlayer of the insulator 240 covers all the display units 250 a and thelower layer of the insulator 240 covers all the display units 250 b. Inthe insulator 240, the upper layer and the lower layer may be formedusing the same material or different materials. In addition, in theinsulator 240, the upper layer and/or the lower layer may be formedusing a combination of a plurality of materials. Alternatively, theinsulator 240 may be formed using one elastic and light-transmittingmaterial.

The area of the display region 260A can be increased by stretching theelastic and light-transmitting insulator 240. For example, the stretchof the insulator 240 in directions of arrows enables the display region260A in FIG. 12B1 to change its shape so as to be a display region 260Bin FIG. 12B2.

The insulator 240 can be formed using, for example, vinyl chloride, apolyurethane resin, silicone, or rubber.

The display region 260A in FIG. 12B1 is stretched in the directions ofthe arrows, whereby gaps between the adjacent display units 250 a in theupper layer of the display region 260A are increased. Note that in thecase where the display region 260A including only the display units 250a as pixels is stretched so as to be the display region 260B, the gapsbetween the adjacent display units 250 a are increased, leading to areduction in resolution of the display region 260B.

Thus, the plurality of display units 250 b are provided in the lowerlayer in addition to the display units 250 a in the upper layer in thedisplay region 260A, as illustrated in FIG. 12B1. With such a structure,when the display region 260A is stretched to be the display region 260B,the light-emitting portions 252 of the display units 250 b appear on thedisplay surface side of the display region 260B. That is, thelight-emitting regions of the display units 250 b in the lower layer areincreased by stretching the display region 260A to be the display region260B, which prevents a reduction in display quality of the displayregion 260B. Note that the upper layer and the lower layer of theinsulator 240 are preferably formed using materials with differentdegrees of elasticity. The degrees of elasticity of the materialsincluded in the upper layer and the lower layer are optimized, so thatthe light-emitting portions 252 of the display units 250 b can overlapwith the gaps between the adjacent display units 250 a when the displayregion 260A is stretched to be the display region 260B.

As illustrated in FIG. 12B1, each of the display units 250 b in thelower layer of the display region 260A is preferably provided to overlapwith parts of the four display units 250 a in the upper layer of thedisplay region 260A. The display region 260A having such a structureenables each of the display units 250 b to be positioned in the largestgap between the adjacent display units 250 a in the upper layer when thedisplay region 260A is stretched to be the display region 260B.

Note that the positions of the display units 250 b in the lower layer ofthe display region 260A are not limited to those in the display region260A in FIG. 12B1. For example, in the case where the display region isstretched in predetermined directions, the structure of a display region261A in FIG. 13A1 can be employed. The display region 261A has astructure in which each of the display units 250 b is provided in thelower layer of the display region 261A to overlap with parts of the twodisplay units 250 a in the upper layer. The insulator 240 in such astructure is stretched in the directions of the arrows, whereby thedisplay region 261A in FIG. 13A1 can be a display region 261B in FIG.13A2.

Alternatively, for example, a display unit 255 in FIG. 14A may be usedas each of the pixels provided in the lower layer of the display region.The display unit 255 is smaller than the display unit 250 (display units250 a and 250 b), and includes a circuit 256 including a light-emittingportion 257. FIG. 14B1 illustrates a display region including thedisplay units 255 in the lower layer. A display region 262A has astructure in which a plurality of display units 255 in the lower layeroverlap with parts of the display units 250 a in the upper layer.Specifically, the display region 262A has the structure in which some ofthe display units 255 in the lower layer overlap with two adjacentdisplay units 250 a in the upper layer, and the others in the lowerlayer overlap with the four display units 250 a arranged in adjacent tworows and two columns in the upper layer. The insulator 240 in such astructure is stretched in the directions of the arrows, whereby thedisplay region 262A in FIG. 14B1 can be a display region 262B in FIG.14B2. Note that owing to the use of the display units 255, the displayregion 262A can include more pixels in the lower layer than the displayregion 260A. Thus, the light-emitting area of the display region 262Bobtained by stretching the display region 262A can be larger than thatof the display region 260B obtained by stretching the display region260A. Accordingly, a decrease in resolution is less caused in thedisplay region 262A than in the display region 260A by the stretch.

Next, an example of the electrical connection between the plurality ofdisplay units 250 included in the display region 260A (260B) and leadwirings is described.

FIG. 15A illustrates an example of the electrical connection between thedisplay units 250 (display units 250 a and 250 b) and the wirings in thedisplay region 260A (260B). Note that the wirings in the display region260B are illustrated in FIG. 15A to clearly show the electricalconnection between the display units 250 (display units 250 a and 250 b)and the wirings.

The display region 260A (260B) includes a plurality of signal lines anda plurality of gate lines. Note that in FIG. 15A, a signal line SLa[1],a signal line SLa[2], a signal line SLb[1], a signal line SLb[2], a gateline GLa[1], a gate line GLa[2], a gate line GLb[1], and a gate lineGLb[2] are illustrated, and reference numerals of the other wirings areomitted. In this specification, the signal lines SLa[1] and SLa[2] arecollectively referred to as a signal line SLa, the signal lines SLb[1]and SLb[2] are collectively referred to as a signal line SLb, the gatelines GLa[1] and GLa[2] are collectively referred to as a gate line GLa,and the gate lines GLb[1] and GLb[2] are collectively referred to as agate line GLb. Each of the signal line SLa, the signal line SLb, thegate line GLa, and the gate line GLb in FIG. 15A may include a pluralityof wirings. For example, each of the signal line SLa[1] and the gateline GLa[1] is not composed of one wiring but may be composed of aplurality of wirings. In some cases, the wirings referred to as thesignal lines can be replaced with the wirings referred to as the gatelines as appropriate.

The signal line SLa and the gate line GLa are electrically connected tothe plurality of display units 250 a included in the upper layer of thedisplay region 260A (260B). The signal line SLb and the gate line GLbare electrically connected to the plurality of display units 250 bincluded in the lower layer of the display region 260A (260B).

FIG. 15B1 is a cross-sectional view of the display region 260A in FIG.15A, and FIG. 15B2 is a cross-sectional view of the display region 260Bin FIG. 15A. FIG. 15B1 shows cross sections taken along thedashed-dotted lines P1-P2 and P3-P4 in the display region 260A in FIG.15A. FIG. 15B2 shows cross sections taken along the dashed-dotted linesP1-P2 and P3-P4 in the display region 260B obtained by stretching thedisplay region 260A in FIG. 15A. Note that the cross section taken alongthe dashed-dotted line P1-P2 shows only the upper layer of the displayregion 260A (260B), and the cross section taken along the dashed-dottedline P3-P4 shows only the lower layer of the display region 260A (260B).

That is, the signal line SLa is electrically connected to the displayunits 250 a and thus is included in the upper layer, and the signal lineSLb is electrically connected to the display units 250 b and thus isincluded in the lower layer. In addition, the signal lines SLa and SLbare formed using an elastic conductive material, which enables thedisplay region 260A in FIG. 15B1 to be stretched to be the displayregion 260B in FIG. 15B2. When the display region 260A in FIG. 15B1 isstretched to be the display region 260B in FIG. 15B2, the gaps betweenthe adjacent display units 250 a are increased, resulting in an increasein the light-emitting areas of the light-emitting elements of thedisplay units 250 b overlapping with parts of the gaps between theadjacent display units 250 a.

Similarly, the gate lines GLa and GLb are formed using an elasticconductive material, which enables the display region 260A to bestretched to be the display region 260B.

A wiring routing way in the display region 260A (260B) is not limited tothe way described using the display region 260A (260B) in FIGS. 15A,15B1, and 15B2. For example, one of a plurality of signal lines SLa inthe upper layer and one of a plurality of signal lines SLb in the lowerlayer may be combined into one wiring. FIG. 16A illustrates an exampleof a display region in such a case. In the display region 260A (260B) inFIG. 16A, the signal lines SLa[1] and SLb[1] are combined into onesignal line SL[1], and the signal lines SLa[2] and SLb[2] are combinedinto one signal line SL[2]. Note that also in the signal lines not shownwith reference numerals in FIG. 16A, one of the signal lines SLa in theupper layer and one of the signal lines SLb in the lower layer arecombined into one wiring. In this specification, the signal linesincluded in the display region 260A (260B) in FIGS. 16A, 16B1, and 16B2are collectively referred to as a signal line SL. Note that a combinedwiring in this paragraph means a wiring formed using one wiring or awiring formed using a plurality of wirings.

FIG. 16B1 is a cross-sectional view of the display region 260A in FIG.16A, and FIG. 16B2 is a cross-sectional view of the display region 260Bin FIG. 16A. FIG. 16B1 is the cross-sectional view taken along thedashed-dotted line Q1-Q2 in the display region 260A in FIG. 16A. FIG.16B2 is the cross-sectional view taken along the dashed-dotted lineQ1-Q2 in the display region 260B obtained by stretching the displayregion 260A in FIG. 16A.

In FIG. 16A, the signal line SL electrically connects the display units250 a in the upper layer to the display units 250 b in the lower layeras illustrated in FIGS. 16B1 and 16B2.

The signal line SL is formed using an elastic conductive material, whichenables the display region 260A in FIG. 16B1 to be stretched to be thedisplay region 260B in FIG. 16B2. When the display region 260A in FIG.16B1 is stretched to be the display region 260B in FIG. 16B2, the gapsbetween the adjacent display units 250 a are increased, resulting in anincrease in the light-emitting areas of the light-emitting elements ofthe display units 250 b overlapping with parts of the gaps between theadjacent display units 250 a.

Similarly, the gate lines GLa and GLb are formed using an elasticconductive material, which enables the display region 260A to bestretched to be the display region 260B. The gate lines GLa and GLb canbe combined into one wiring (not illustrated) as in the signal line SL.

Next, an example of a driver circuit for driving the display region 260A(260B) is described.

FIG. 17A illustrates a display device 300 including a display region260. The display device 300 includes a driver region 270 and a driverregion 280 in addition to the display region 260. Here, the driverregion 270 functions as a source driver for driving the display region260, and the driver region 280 functions as a gate driver for drivingthe display region 260.

For another example, the display device 300 may have a structure inwhich the driver region 270 functions as a gate driver for driving thedisplay region 260 and the driver region 280 functions as a sourcedriver for driving the display region 260.

The driver region 270 includes a plurality of driver circuit units 271.Some of the plurality of driver circuit units 271 are electricallyconnected to the display units 250 a through the signal line SLa, andthe others are electrically connected to the display units 250 b throughthe signal line SLb. The plurality of driver circuit units 271 have afunction of supplying a signal for an image to be displayed on thedisplay region 260 to the display region 260 through the signal linesSLa and SLb.

The plurality of driver circuit units 271 are aligned in a line, and theadjacent driver circuit units 271 are electrically connected to eachother with a wiring 272. Note that the number of wirings 272 may be one,or two or more.

The driver region 280 includes a plurality of driver circuit units 281.Some of the plurality of driver circuit units 281 are electricallyconnected to the display units 250 a through the gate line GLa, and theothers are electrically connected to the display units 250 b through thegate line GLb. The plurality of driver circuit units 281 have a functionof supplying a selection signal to pixels included in the display region260 through the gate lines GLa and GLb.

The plurality of driver circuit units 281 are aligned in a line, and theadjacent driver circuit units 281 are electrically connected to eachother with a wiring 282. Note that the number of wirings 282 may be one,or two or more.

The wirings 272 and 282 are formed using an elastic conductive materialas in the signal lines SLa and SLb and the gate lines GLa and GLb.Accordingly, the elastic wirings 272 and 282 increase the gaps betweenthe adjacent driver circuit units 271 and the gaps between the adjacentdriver circuit units 281. Thus, the display device 300 in FIG. 17A canhave the shape in FIG. 17B when stretched.

Although the driver region 270 includes the plurality of driver circuitunits 271 in FIG. 17A, one embodiment of the present invention is notlimited thereto. For example, the driver region 270 may include onedriver circuit unit 271 (not illustrated). Similarly, although thedriver region 280 includes the plurality of driver circuit units 281 inFIG. 17A, the driver region 280 may include one driver circuit unit 281(not illustrated).

In the case where the circuit area of the driver circuit unit 271 and/orthe driver circuit unit 281 becomes large, the driver region 270 and/orthe driver region 280 may have a two-layer structure as in the displayregion 260. Specifically, in the driver region having the two-layerstructure, the adjacent driver circuit units may partly overlap witheach other.

A driver region 270A and a driver region 280A in a display device 300Ain FIG. 18A each have a two-layer structure. The driver region 270Aincludes a plurality of driver circuit units 271A, and the driver region280A includes a plurality of driver circuit units 281A. The drivercircuit units 271A in the upper layer of the driver region 270A areelectrically connected to the display units 250 a through the signalline SLa, and the driver circuit units 271A in the lower layer of thedriver region 270A are electrically connected to the display units 250 bthrough the signal line SLb. Similarly, the driver circuit units 281A inthe upper layer of the driver region 280A are electrically connected tothe display units 250 a through the gate line GLa, and the drivercircuit units 281A in the lower layer of the driver region 280A areelectrically connected to the display units 250 b through the gate lineGLb.

FIG. 18B1 is a cross-sectional view taken along the dashed-dotted lineR1-R2 in FIG. 18A. As described above, in the driver region 270A, theadjacent driver circuit units 271A partly overlap with each other. Inaddition, the adjacent driver circuit units 271A are electricallyconnected to each other with the elastic wiring 272.

Note that when the display device 300A is stretched, the cross sectiontaken along the dashed-dotted line R1-R2 in FIG. 18B1 changes to that inFIG. 18B2. With the driver region 270A having the two-layer structureand the elastic wiring 272 illustrated in FIG. 18B1, the display device300A can be stretched even when the circuit area of the driver circuitunit 271 is large.

For the description of stretching the driver region 280A, refer to thedescription of stretching the driver region 270A.

The structure examples described in this embodiment can be combined witheach other as appropriate.

<Manufacturing Method Example>

Next, an example of a method for manufacturing the display region 260Ais described with reference to FIGS. 19A to 19C, FIGS. 20A and 20B,FIGS. 21A and 21B, FIG. 22 , and FIG. 23 .

First, an insulator 321 is formed over a substrate 311 (see FIG. 19A).

The substrate 311 can be formed using any of a variety of materials suchas glass, quartz, a resin, a metal, an alloy, and a semiconductor. Whenthe substrate 311 is formed using a flexible material, any of theabove-described materials that is thin enough to be flexible may beused, for example.

The insulator 321 can be used as a barrier layer that prevents diffusionof impurities contained in the substrate 311 into a transistor and adisplay element formed later. For example, the insulator 321 preferablyprevents moisture and the like contained in the substrate 311 fromdiffusing into the transistor and the display element in a heating stepperformed in the manufacturing process of the display region 260A. Thus,the insulator 321 preferably has a high barrier property.

For the insulator 321, an inorganic insulating film such as a siliconnitride film, a silicon oxynitride film, a silicon oxide film, a siliconnitride oxide film, an aluminum oxide film, or an aluminum nitride filmcan be used, for example. Alternatively, a hafnium oxide film, anyttrium oxide film, a zirconium oxide film, a gallium oxide film, atantalum oxide film, a magnesium oxide film, a lanthanum oxide film, acerium oxide film, a neodymium oxide film, or the like may be used. Astack including two or more of the above insulating films may also beused. It is particularly preferable that a silicon nitride film beformed over the substrate 311 and a silicon oxide film be formed overthe silicon nitride film.

The inorganic insulating film is preferably formed at high temperaturesbecause the film can have higher density and a higher barrier propertyas the deposition temperature becomes higher. The deposition temperatureof the insulator 321 is preferably lower than or equal to the uppertemperature limit of the substrate 311.

After the insulator 321 is formed over the substrate 311, a circuit, awiring, and the like are formed over the insulator 321 (see FIG. 19B).In FIG. 19B, a transistor 401 is formed over the substrate 311.

There is no particular limitation on the structure of the transistor inthe display region 260A. For example, a planar transistor, a staggeredtransistor, or an inverted staggered transistor may be used. A top-gatetransistor or a bottom-gate transistor may also be used. Gate electrodesmay be provided above and below a channel.

Described here is the case where a bottom-gate transistor including ametal oxide 350 is formed as the transistor 401. The metal oxide 350 canfunction as a semiconductor layer of the transistor 401. Note that themetal oxide described here can function as an oxide semiconductor.

In this embodiment, an oxide semiconductor is used as a semiconductor ofthe transistor. The oxide semiconductor is a semiconductor materialhaving a wider band gap and a lower carrier density than silicon; thus,the off-state current of a transistor including the oxide semiconductorin a channel formation region can be reduced.

The transistor 401 is preferably formed at a temperature lower than thetemperature of the heat treatment.

Here, a specific example of a method for forming the transistor 401 isdescribed.

First, a conductor 341 is formed over the insulator 321. The conductor341 can be formed in the following manner: a conductive film is formed,a resist mask is formed, the conductive film is etched, and the resistmask is removed.

The substrate temperature during the formation of the conductive film ispreferably higher than or equal to room temperature and lower than orequal to 350° C., further preferably higher than or equal to roomtemperature and lower than or equal to 300° C.

The conductors included in the display region 260A can each have asingle-layer structure or a stacked-layer structure including any ofmetals such as aluminum, titanium, chromium, nickel, copper, yttrium,zirconium, molybdenum, silver, tantalum, and tungsten or an alloycontaining any of these metals as its main component. Alternatively, alight-transmitting conductive material such as indium oxide, indium tinoxide (ITO), indium oxide containing tungsten, indium zinc oxidecontaining tungsten, indium oxide containing titanium, ITO containingtitanium, indium zinc oxide, zinc oxide (ZnO), ZnO containing gallium,or ITO containing silicon may be used. Alternatively, a semiconductorsuch as an oxide semiconductor or polycrystalline silicon whoseresistance is lowered by adding an impurity element, for example, orsilicide such as nickel silicide may be used. A film including graphenemay be used as well. The film including graphene can be formed, forexample, by reducing a film including graphene oxide. A semiconductorsuch as an oxide semiconductor containing an impurity element may beused. Alternatively, the conductors may be formed using a conductivepaste of silver, carbon, copper, or the like or a conductive polymersuch as a polythiophene. A conductive paste is preferable because it isinexpensive. A conductive polymer is preferable because it is easilyapplied.

Then, an insulator 322 is formed over the conductor 341 and theinsulator 321. For the material that can be used for the insulator 322,refer to the description of the inorganic insulating film that can beused for the insulator 321.

The insulator 322 is formed at a temperature lower than or equal to theupper temperature limit of the substrate 311. The insulator 322 ispreferably formed at a temperature lower than the temperature of theheat treatment.

Next, the metal oxide 350 is formed over the insulator 322 to overlapwith part of the conductor 341. The metal oxide 350 can be formed in thefollowing manner: a metal oxide film is formed, a resist mask is formed,the metal oxide film is etched, and the resist mask is removed.

The substrate temperature during the formation of the metal oxide filmis preferably lower than or equal to 350° C., further preferably higherthan or equal to room temperature and lower than or equal to 200° C.,still further preferably higher than or equal to room temperature andlower than or equal to 130° C.

The metal oxide film can be formed using one or both of an inert gas andan oxygen gas. Note that there is no particular limitation on the flowratio of oxygen (the partial pressure of oxygen) in the step of formingthe metal oxide film. In the case where a transistor having highfield-effect mobility is obtained, the flow ratio of oxygen (the partialpressure of oxygen) in the step of forming the metal oxide film ispreferably higher than or equal to 0% and lower than or equal to 30%,further preferably higher than or equal to 5% and lower than or equal to30%, still further preferably higher than or equal to 7% and lower thanor equal to 15%.

The metal oxide film preferably contains at least indium or zinc. Inparticular, indium and zinc are preferably contained.

The energy gap of the metal oxide is preferably 2 eV or more, furtherpreferably 2.5 eV or more, and still further preferably 3 eV or more.The use of such a metal oxide having a wide energy gap leads to areduction in off-state current of a transistor.

The metal oxide film can be formed by a sputtering method.Alternatively, a PLD method, a PECVD method, a thermal CVD method, anALD method, a vacuum evaporation method, or the like may be used.

Then, a conductor 342 a and a conductor 342 b are formed over theinsulator 322 and the metal oxide 350. Note that part of the conductor342 a and/or part of the conductor 342 b may be included in a regionoverlapping with the metal oxide 350. The conductors 342 a and 342 b canbe formed in the following manner: a conductive film is formed, a resistmask is formed, the conductive film is etched, and the resist mask isremoved.

Note that during the processing for forming the conductor 342 a and theconductor 342 b, the metal oxide 350 might be partly etched to be thinin a region not covered by the resist mask.

The substrate temperature during the formation of the conductive film ispreferably higher than or equal to room temperature and lower than orequal to 350° C., further preferably higher than or equal to roomtemperature and lower than or equal to 300° C.

In the above manner, the transistor 401 can be fabricated. In thetransistor 401, part of the conductor 341 functions as a gate, part ofthe insulator 322 functions as a gate insulating layer, the conductor342 a functions as one of a source and a drain, and the conductor 342 bfunctions as the other of the source and the drain.

A conductor 343 is formed over the insulator 322. The conductor 343 canbe formed at the same time as the conductors 342 a and 342 b. In thecase where the conductor 343 is formed using a material different fromthat of the conductors 342 a and 342 b, the conductor 343 may be formedindependently of the conductors 342 a and 342 b. The conductor 343functions as a wiring electrically connecting a display unit, anelement, a circuit, and the like to each other. Part of the conductor343 also functions as a terminal that transmits and receives anelectrical signal to and from the outside.

Next, an insulator 323 that covers the transistor 401 is formed. Theinsulator 323 can be formed in a manner similar to that of the insulator321.

It is preferable to use an oxide insulating film formed in anoxygen-containing atmosphere, such as a silicon oxide film or a siliconoxynitride film, for the insulator 323. An insulating film with lowoxygen diffusibility and oxygen permeability, such as a silicon nitridefilm, is preferably stacked over the silicon oxide film or the siliconoxynitride film. The oxide insulating film formed in anoxygen-containing atmosphere can easily release a large amount of oxygenby heating. When a stack including such an oxide insulating film thatreleases oxygen and such an insulating film with low oxygendiffusibility and oxygen permeability is heated, oxygen can be suppliedto the metal oxide 350. As a result, oxygen vacancies in the metal oxide350 can be filled and defects at the interface between the metal oxide350 and the insulator 323 can be repaired, leading to a reduction indefect levels. Accordingly, an extremely highly reliable display devicecan be manufactured.

Then, an insulator 324 is formed over the insulator 323. The displayelement is formed on the insulator 324 in a later step; thus, theinsulator 324 preferably functions as a planarization layer. For theinsulator 324, refer to the description of the organic insulating filmor the inorganic insulating film that can be used for the insulator 321.

The insulator 324 is formed at a temperature lower than or equal to theupper temperature limit of the substrate 311. The insulator 324 ispreferably formed at a temperature lower than the temperature of theheat treatment.

Next, an opening 361 reaching the conductor 342 b and an opening 362reaching the conductor 343 are formed in the insulators 323 and 324 (seeFIG. 19C).

Then, a conductor 344 a is formed over the insulator 324 and theconductor 342 b through the opening 361. Part of the conductor 344 afunctions as a pixel electrode of a light-emitting element 370 describedlater. The conductor 344 a can be formed in the following manner: aconductive film is formed, a resist mask is formed, the conductive filmis etched, and the resist mask is removed.

Concurrently with the conductor 344 a, a conductor 344 b is formed overthe conductor 343 through the opening 362. Note that the conductor 344 bis not necessarily formed.

The substrate temperature during the formation of the conductive film ispreferably higher than or equal to room temperature and lower than orequal to 350° C., further preferably higher than or equal to roomtemperature and lower than or equal to 300° C.

An insulator 325 that covers an end portion of the conductor 344 a isformed. For the insulator 325, refer to the description of the inorganicinsulating film that can be used for the insulator 321. Alternatively,the insulator 325 can be formed using an organic insulating film.

The insulator 325 is formed at a temperature lower than or equal to theupper temperature limit of the substrate 311. The insulator 325 ispreferably formed at a temperature lower than the temperature of theheat treatment.

Next, the light-emitting element 370 is formed over the formationsubstrate in FIG. 19C (see FIG. 20A).

For formation of the light-emitting element 370, first, an EL layer 371is formed over the conductor 344 a and the insulator 325.

The EL layer 371 can be formed by an evaporation method, a coatingmethod, a printing method, a discharge method, or the like. In the casewhere the EL layer 371 is formed for each individual pixel, anevaporation method using a shadow mask such as a metal mask, an ink-jetmethod, or the like can be used. In the case of sharing the EL layer 371by some pixels, an evaporation method not using a metal mask can beused.

Either a low molecular compound or a high molecular compound can be usedfor the EL layer 371, and an inorganic compound may also be used.

Note that for the details of the EL layer 371, refer to the descriptionof an EL layer 1103 in Embodiment 5.

Next, a conductor 345 is formed over the insulator 325 and the EL layer371. Part of the conductor 345 functions as a common electrode of thelight-emitting element 370.

The conductor 345 can be formed by an evaporation method, a sputteringmethod, or the like.

The conductor 345 is formed at a temperature that is lower than or equalto the upper temperature limit of the substrate 311 and lower than orequal to the upper temperature limit of the EL layer 371. The conductor345 is preferably formed at a temperature lower than the temperature ofthe heat treatment.

As the conductor 345, a light-transmitting conductor is used. Examplesof the light-transmitting conductor include metal oxides such as indiumtin oxide (ITO), indium tin oxide containing silicon or silicon oxide,indium oxide-zinc oxide, indium oxide-tin oxide containing titanium,indium titanium oxide, and indium oxide containing tungsten oxide andzinc oxide. As the conductor 345, indium tin oxide is particularlypreferable.

In the above manner, the light-emitting element 370 can be formed. Inthe light-emitting element 370, the conductor 344 a part of whichfunctions as a pixel electrode, the EL layer 371, and the conductor 345part of which functions as a common electrode are stacked. Note that atop-emission light-emitting element is formed as the light-emittingelement 370 here.

Next, an insulator 326 is formed to cover the conductor 345. Theinsulator 326 functions as a protective layer that prevents diffusion ofimpurities such as water into the light-emitting element 370. Thelight-emitting element 370 is sealed with the insulator 326. After theconductor 345 is formed, the insulator 326 is preferably formed withoutexposure to the air.

The insulator 326 is formed at a temperature that is lower than or equalto the upper temperature limit of the substrate 311 and lower than orequal to the upper temperature limit of the light-emitting element 370.The insulator 326 is preferably formed at a temperature lower than thetemperature of the heat treatment.

The insulator 326 preferably includes an inorganic insulating film witha high barrier property that can be used for the insulator 321, forexample. A stack including an inorganic insulating film and an organicinsulating film can also be used.

The insulator 326 can be formed by an ALD method, a sputtering method,or the like. An ALD method and a sputtering method are preferablebecause a film can be formed at low temperatures. An ALD method ispreferable because the coverage with the insulator 326 is improved.

A structure where the components up to the insulator 326 are formed overthe substrate 311 corresponds to the display unit 250.

To describe an example of a method for manufacturing the display region260A having a two-layer structure below, the display unit 250 in thelower layer is referred to as the display unit 250 b, and the displayunits 250 in the upper layer are referred to as a display unit 250 a[1]and a display unit 250 a[2].

The display unit 250 b is provided over a support substrate 301 (seeFIG. 20B). The substrate 311 is bonded to the support substrate 301preferably with an adhesive resin layer or the like. Note that the resinlayer is not illustrated in FIG. 20B. The support substrate 301 isincluded in the insulator 240.

The support substrate 301 is formed using an elastic material. Forexample, the support substrate 301 can be formed using a thermosettingelastomer, a thermoplastic elastomer, or the like.

Next, a conductor 380 is formed over the conductor 344 b and the supportsubstrate 301 (see FIG. 21A). The conductor 380 corresponds to thesignal line, the gate line, or the like described in the structureexamples.

The conductor 380 preferably has elasticity. The conductor 380 can beformed using a conductive paste of silver, carbon, copper, or the like,a conductive polymer such as polythiophene, or the like.

Then, a protective layer 390 is formed over the support substrate 301and the display unit 250 b over the substrate 311 (see FIG. 21B). Notethat the protective layer 390 is included in the insulator 240.

As the protective layer 390, a light-transmitting and elastic insulatoris used. For example, the protective layer 390 can be formed using vinylchloride, a polyurethane resin, or the like. In addition to alight-transmitting property and elasticity, the protective layer 390preferably has adhesiveness for bonding the support substrate 301 to thedisplay unit 250 b.

Next, a substrate 302 is provided over the protective layer 390 (seeFIG. 22 ). The substrate 302 is formed using a light-transmitting andelastic material. In addition, the degrees of elasticity of thesubstrate 302 and the support substrate 301 are preferably differentfrom each other. Note that the substrate 302 is included in theinsulator 240.

Then, the display units 250 a[1] and 250 a[2], which can be formed in amanner similar to that of the display unit 250 b, are formed over thesubstrate 302 (see FIG. 23 ). The display units 250 a[1] and 250 a[2]each include a transistor, a light-emitting element, and a wiring as inthe display unit 250 b.

The display units 250 a[1] and 250 a[2] are preferably formed over thesubstrate 302 so that part of the light-emitting element 370 of thedisplay unit 250 b overlaps with part of the gap between the displayunits 250 a[1] and 250 a[2].

After the formation of the display units 250 a[1] and 250 a[2], aconductor 381 is formed as a wiring in a manner similar to that of theconductor 380 electrically connected to the display unit 250 b. Formaterials that can be used for the conductor 381, refer to thedescription of the materials that can be used for the conductor 380.

After the formation of the conductor 381, a protective layer 391 isformed over the display units 250 a[1] and 250 a[2], the conductor 381,and the substrate 302 in a manner similar to that of the protectivelayer 390 formed over the display unit 250 b. Note that the materialsthat can be used for the protective layer 391 preferably have the degreeof elasticity different from that of elasticity of the materials thatcan be used for the protective layer 390. The protective layer 391 isincluded in the insulator 240.

After the formation of the protective layer 391, a substrate 303 isprovided over the protective layer 391 in a manner similar to that ofthe substrate 302 provided over the protective layer 390. The substrate303 is formed using a light-transmitting and elastic material. Inaddition, the degrees of elasticity of the substrate 303, the supportsubstrate 301, and the substrate 302 are preferably different from eachother. Note that the substrate 303 is included in the insulator 240. Inthe example of a method for manufacturing the display region 260A, thesubstrate 303 is not necessarily provided.

Through the above steps, the display region 260A can be manufactured.

The display regions 261A and 262A can be manufactured in a mannersimilar to that of the display region 260A by referring to theabove-described manufacturing method example.

Although the display unit 250 is formed over the support substrate 301in this manufacturing method example, a method for manufacturing thedisplay device of one embodiment of the present invention is not limitedthereto.

For example, before the transistor 401, the light-emitting element 370,and the like are formed, the substrate 311 may be provided over thesupport substrate 301. In this case, the deposition temperature of theinsulators, conductors, metal oxides, and the like included in thedisplay unit 250 and the temperature of the heat treatment performed onthe transistor 401 and the like are preferably lower than the uppertemperature limits of the support substrate 301 and the substrate 311.For another example, instead of the substrate 311 provided over thesupport substrate 301, an insulator formed by a sputtering method, apulsed laser deposition (PLD) method, a plasma-enhanced chemical vapordeposition (PECVD) method, a thermal CVD method, an atomic layerdeposition (ALD) method, a vacuum evaporation method, or the like may beused. In that case, the insulator may be formed using a materialdifferent from that of the insulator 321 and stacked with the insulator321; alternatively, the insulators may be formed using the same materialas the insulator 321 and successively formed.

For example, one embodiment of the present invention may employ amanufacturing method in which the display unit 250 is formed over apolyimide film or the like that is provided over the substrate 311 inadvance by application of polyimide or the like as an organic film, andthe display unit 250 is separated from the polyimide film andtransferred to the support substrate 301. After the display unit 250 istransferred to the support substrate 301, the conductor 380 and theprotective layer 390 may be formed. Instead of the organic film such asa polyimide film, an inorganic film such as a tungsten film can be used,in some cases. FIG. 24A illustrates a step of providing the display unit250, which is separated from the organic film or the inorganic film,over the support substrate 301. In some cases, the residue of theorganic film or the inorganic film are attached to the insulator 321 onthe bottom surface of the display unit 250 separated from the organicfilm or the inorganic film.

After the display unit 250 is separated by the above-described method,the display unit 250 may be transferred to a flexible substrate 315 andthen the substrate 315 may be bonded to the support substrate 301 (seeFIG. 24B). In that case, the circuit 251 is positioned on the substrate315; thus, the substrate 315 is preferably formed using a material withlow elasticity, which prevents the circuit 251 from being damaged (e.g.,a crack) by the stretch of the substrate 315.

With this method, the display unit 250 is formed over the substrateprovided with the polyimide film or the like; thus, the heat treatmentfor forming the display unit 250 does not need to be performed on thesupport substrate 301 and the substrate 315 to which the display unit250 is transferred. That is, the temperatures of the heat treatmentperformed on the insulators, conductors, and metal oxides included inthe display unit 250 are not limited to the upper temperature limits ofthe support substrate 301 and the substrate 315 to which the displayunit 250 is transferred. The support substrate 301 can be formed using amaterial with low heat resistance because the support substrate 301 isnot affected by the heat treatment for forming the display unit 250.

The manufacturing method example described in this embodiment enables adisplay device whose display quality does not degrade even when the areaof the display region is increased by the stretch.

Note that this embodiment can be combined with other embodiments and/oran example in this specification as appropriate.

Embodiment 4

In this embodiment, examples of electronic devices each including thedisplay device 300 in Embodiment 3 are described.

Example 1

FIG. 25A illustrates an electronic device including the display device300. An electronic device 7000 can be used as an information terminal orelectronic paper, for example. The electronic device 7000 includes thedisplay device 300 and thus can be stretched by pulling with fingers7001, as illustrated in FIG. 25A. Owing to its elasticity, theelectronic device 7000 can be attached to a structure body having acurved surface or the like. When the electronic device 7000 includingthe display device 300 as a light-emitting device is attached to astructure body having a curved surface or the like, the electronicdevice 7000 can be used as a lighting device.

Example 2

FIG. 25B illustrates a smart watch which is one of wearable terminals.The smart watch includes a housing 5901, a display portion 5902,operation buttons 5903, an operator 5904, a band 5905, and the like. Thedisplay device 300 can be used for the display portion 5902 of the smartwatch. When the display portion 5902 has a convex surface, for example,the stretched display device 300 is attached to the convex surface,whereby the convex display portion 5902 can be obtained.

Example 3

FIG. 25C illustrates clothing to which the display device 300 isattached. Clothing 5801 includes a display portion 5802 and the like.The display device 300 can be used for the display portion 5802. Sincethe display device 300 can be stretched, the display device 300 can beattached to the elastic clothing 5801. In addition, the display portion5802 can be used as a lighting device.

FIG. 25C illustrates an example in which the display portion 5802 isattached to a chest portion of the clothing 5801; however, oneembodiment of the present invention is not limited to this example. Forexample, the display portion 5802 may be attached to a sleeve portion, abelly portion, a back portion, and the like. Although the clothing 5801in FIG. 25C is a shirt, the clothing 5801 can also be clothes such as ajacket, underwear, and pants, accessories such as shoes, a hat, and awristband, and the like.

Example 4

FIG. 25D illustrates a windshield and its vicinity inside a car, whichis one of moving vehicles. The display device 300 can be used fordisplay panels 5701, 5702, and 5703 attached to a dashboard, a displaypanel 5704 attached to a pillar, and the like illustrated in FIG. 25D.

The display panels 5701 to 5703 can display a variety of kinds ofinformation such as navigation information, a speedometer, a tachometer,a mileage, a fuel meter, a gearshift indicator, and air-conditionsetting. The content, layout, or the like of the display on the displaypanels can be changed freely to suit the user's preferences, so that thedesign can be improved. The display panels 5701 to 5703 can also be usedas lighting devices.

The display panel 5704 can compensate for the view obstructed by thepillar (blind areas) by showing an image taken by an imaging unitprovided for the car body. That is, showing an image taken by an imagingunit provided on the outside of the car body leads to elimination ofblind areas and enhancement of safety. In addition, showing an image soas to compensate for the area which a driver cannot see makes itpossible for the driver to confirm safety easily and comfortably. Thedisplay panel 5704 can also be used as a lighting device.

Example 5

FIGS. 26A and 26B each illustrate an example of a digital signage thatcan be attached to a wall. FIG. 26A illustrates a digital signage 6300Aattached to a wall 6301.

Here, the case where the digital signage 6300A includes the displaydevice 300 in Embodiment 3 is described. The digital signage 6300A inFIG. 26A that includes the display device 300 can change its shape so asto be a digital signage 6300B in FIG. 26B by the stretch. The digitalsignage 6200A in FIGS. 11A and 11B in Embodiment 2 can be stretched inthe vertical direction or the horizontal direction, and the aspect ratioof the digital signage 6300A (6300B) in FIGS. 26A and 26B can be freelychanged depending on the contents displayed on the digital signage.

Note that this embodiment can be combined with other embodiments and/oran example in this specification as appropriate.

Embodiment 5

In this embodiment, light-emitting elements that can be used for thedisplay units in Embodiment 1 are described with reference to FIGS. 27Ato 27D.

<Basic Structure of Light-Emitting Element>

A basic structure of a light-emitting element will be described. FIG.27A illustrates a light-emitting element including, between a pair ofelectrodes, an EL layer having a light-emitting layer. Specifically, theEL layer 1103 is provided between a first electrode 1101 and a secondelectrode 1102.

FIG. 27B illustrates a light-emitting element that has a stacked-layerstructure (tandem structure) in which a plurality of EL layers (two ELlayers 1103 a and 1103 b in FIG. 27B) are provided between a pair ofelectrodes and a charge-generation layer 1104 is provided between the ELlayers. With the use of such a tandem light-emitting element, alight-emitting device which can be driven at low voltage with low powerconsumption can be obtained.

The charge-generation layer 1104 has a function of injecting electronsinto one of the EL layers (1103 a or 1103 b) and injecting holes intothe other of the EL layers (1103 b or 1103 a) when voltage is appliedbetween the first electrode 1101 and the second electrode 1102. Thus,when voltage is applied in FIG. 27B such that the potential of the firstelectrode 1101 is higher than that of the second electrode 1102, thecharge-generation layer 1104 injects electrons into the EL layer 1103 aand injects holes into the EL layer 1103 b.

Note that in terms of light extraction efficiency, the charge-generationlayer 1104 preferably has a property of transmitting visible light(specifically, the charge-generation layer 1104 has a visible lighttransmittance of 40% or more). The charge-generation layer 1104functions even when it has lower conductivity than the first electrode1101 or the second electrode 1102.

FIG. 27C illustrates a stacked-layer structure of the EL layer 1103 inthe light-emitting element which can be used in the display device ofone embodiment of the present invention. In this case, the firstelectrode 1101 is regarded as functioning as an anode. The EL layer 1103has a structure in which a hole-injection layer 1111, a hole-transportlayer 1112, a light-emitting layer 1113, an electron-transport layer1114, and an electron-injection layer 1115 are stacked in this orderover the first electrode 1101. Even in the case where a plurality of ELlayers are provided as in the tandem structure illustrated in FIG. 27B,the layers in each EL layer are sequentially stacked from the anode sideas described above. When the first electrode 1101 is a cathode and thesecond electrode 1102 is an anode, the stacking order is reversed.

The light-emitting layer 1113 included in the EL layers (1103, 1103 a,and 1103 b) contains an appropriate combination of a light-emittingsubstance and a plurality of substances, so that fluorescence orphosphorescence of a desired emission color can be obtained. Thelight-emitting layer 1113 may have a stacked-layer structure havingdifferent emission colors. In that case, the light-emitting substanceand other substances are different between the stacked light-emittinglayers. Alternatively, the plurality of EL layers (1103 a and 1103 b) inFIG. 27B may exhibit their respective emission colors. Also in thatcase, the light-emitting substance and other substances are differentbetween the light-emitting layers.

In the light-emitting element of one embodiment of the presentinvention, for example, a micro optical resonator (microcavity)structure in which the first electrode 1101 is a reflective electrodeand the second electrode 1102 is a transflective electrode can beemployed in FIG. 27C, whereby light emission from the light-emittinglayer 1113 in the EL layer 1103 can be resonated between the electrodesand light emission obtained through the second electrode 1102 can beintensified.

Note that when the first electrode 1101 of the light-emitting element isa reflective electrode having a structure in which a reflectiveconductive material and a light-transmitting conductive material(transparent conductive film) are stacked, optical adjustment can beperformed by controlling the thickness of the transparent conductivefilm. Specifically, when the wavelength of light obtained from thelight-emitting layer 1113 is λ, the distance between the first electrode1101 and the second electrode 1102 is preferably adjusted to around mλ/2(m is a natural number).

To amplify desired light (wavelength: X) obtained from thelight-emitting layer 1113, the optical path length from the firstelectrode 1101 to a region where the desired light is obtained in thelight-emitting layer 1113 (light-emitting region) and the optical pathlength from the second electrode 1102 to the region where the desiredlight is obtained in the light-emitting layer 1113 (light-emittingregion) are preferably adjusted to around (2m′+1)λ/4 (m′ is a naturalnumber). Here, the light-emitting region means a region where holes andelectrons are recombined in the light-emitting layer 1113.

By such optical adjustment, the spectrum of specific monochromatic lightobtained from the light-emitting layer 1113 can be narrowed and lightemission with high color purity can be obtained.

In that case, the optical path length between the first electrode 1101and the second electrode 1102 is, to be exact, the total thickness froma reflective region in the first electrode 1101 to a reflective regionin the second electrode 1102. However, it is difficult to exactlydetermine the reflective regions in the first electrode 1101 and thesecond electrode 1102; thus, it is assumed that the above effect can besufficiently obtained wherever the reflective regions may be set in thefirst electrode 1101 and the second electrode 1102. Furthermore, theoptical path length between the first electrode 1101 and thelight-emitting layer 1113 emitting the desired light is, to be exact,the optical path length between the reflective region in the firstelectrode 1101 and the light-emitting region in the light-emitting layer1113 emitting the desired light. However, it is difficult to preciselydetermine the reflective region in the first electrode 1101 and thelight-emitting region in the light-emitting layer emitting the desiredlight; thus, it is assumed that the above effect can be sufficientlyobtained wherever the reflective region and the light-emitting regionmay be set in the first electrode 1101 and the light-emitting layeremitting the desired light.

The light-emitting element in FIG. 27C has a microcavity structure, sothat light (monochromatic light) with different wavelengths can beextracted even if the same EL layer is used. Thus, separate coloring forobtaining a plurality of emission colors (e.g., R, G, and B) is notnecessary. Therefore, high resolution can be easily achieved. Note thata combination with coloring layers (color filters) is also possible.Furthermore, emission intensity of light with a specific wavelength inthe front direction can be increased, whereby power consumption can bereduced.

In the light-emitting element of one embodiment of the presentinvention, at least one of the first electrode 1101 and the secondelectrode 1102 is a light-transmitting electrode (e.g., a transparentelectrode or a transflective electrode). In the case where thelight-transmitting electrode is a transparent electrode, the transparentelectrode has a visible light transmittance of higher than or equal to40%. In the case where the light-transmitting electrode is atransflective electrode, the transflective electrode has a visible lightreflectance of higher than or equal to 20% and lower than or equal to80%, and preferably higher than or equal to 40% and lower than or equalto 70%. These electrodes preferably have a resistivity of 1×10⁻² Ωcm orless.

Furthermore, when one of the first electrode 1101 and the secondelectrode 1102 is a reflective electrode in the light-emitting elementof one embodiment of the present invention, the visible lightreflectance of the reflective electrode is higher than or equal to 40%and lower than or equal to 100%, and preferably higher than or equal to70% and lower than or equal to 100%. This electrode preferably has aresistivity of 1×10⁻² Ω/cm or less.

<Specific Structure and Fabrication Method of Light-Emitting Element>

Specific structures and specific fabrication methods of light-emittingelements of embodiments of the present invention will be described.Here, a light-emitting element having the tandem structure in FIG. 27Band a microcavity structure will be described with reference to FIG.27D. In the light-emitting element in FIG. 27D, the first electrode 1101is formed as a reflective electrode and the second electrode 1102 isformed as a transflective electrode. Thus, a single-layer structure or astacked-layer structure can be formed using one or more kinds of desiredelectrode materials. Note that the second electrode 1102 is formed afterformation of the EL layer 1103 b, with the use of a material selected asdescribed above. For fabrication of these electrodes, a sputteringmethod or a vacuum evaporation method can be used.

<<First Electrode and Second Electrode>>

As materials used for the first electrode 1101 and the second electrode1102, any of the following materials can be used in an appropriatecombination as long as the functions of the electrodes described abovecan be fulfilled. For example, a metal, an alloy, an electricallyconductive compound, a mixture of these, and the like can beappropriately used. Specifically, an In—Sn oxide (also referred to asITO), an In—Si—Sn oxide (also referred to as ITSO), an In—Zn oxide, anIn—W—Zn oxide, or the like can be used. In addition, it is possible touse a metal such as aluminum (Al), titanium (Ti), chromium (Cr),manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu),gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo),tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt),silver (Ag), yttrium (Y), or neodymium (Nd) or an alloy containing anappropriate combination of any of these metals. It is also possible touse a Group 1 element or a Group 2 element in the periodic table, whichis not described above (e.g., lithium (Li), cesium (Cs), calcium (Ca),or strontium (Sr)), a rare earth metal such as europium (Eu) orytterbium (Yb), an alloy containing an appropriate combination of any ofthese elements, graphene, or the like.

In the light-emitting element in FIG. 27D, when the first electrode 1101is an anode, a hole-injection layer 1111 a and a hole-transport layer1112 a of the EL layer 1103 a are sequentially stacked over the firstelectrode 1101 by a vacuum evaporation method. After the EL layer 1103 aand the charge-generation layer 1104 are formed, a hole-injection layer1111 b and a hole-transport layer 1112 b of the EL layer 1103 b aresequentially stacked over the charge-generation layer 1104 in a similarmanner.

<<Hole-Injection Layer and Hole-Transport Layer>>

The hole-injection layers (1111 a and 1111 b) inject holes from thefirst electrode 1101 that is an anode to the EL layers (1103 a and 1103b) and each contain a material with a high hole-injection property.

As examples of the material with a high hole-injection property,transition metal oxides such as molybdenum oxide, vanadium oxide,ruthenium oxide, tungsten oxide, and manganese oxide can be given.Alternatively, it is possible to use any of the following materials:phthalocyanine-based compounds such as phthalocyanine (abbreviation:H₂Pc) and copper phthalocyanine (abbreviation: CuPc); aromatic aminecompounds such as4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB) andN,N′-bis{4-[bis(3-methylphenyl)amino]phenyl}-diphenyl-(1,1′-biphenyl)-4,4′-diamine(abbreviation: DNTPD); high molecular compounds such aspoly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid)(abbreviation: PEDOT/PSS); and the like.

Alternatively, as the material with a high hole-injection property, acomposite material containing a hole-transport material and an acceptormaterial (an electron-accepting material) can also be used. In thatcase, the acceptor material extracts electrons from the hole-transportmaterial, so that holes are generated in the hole-injection layers (1111a and 1111 b) and the holes are injected into the light-emitting layers(1113 a and 1113 b) through the hole-transport layers (1112 a and 1112b). Note that each of the hole-injection layers (1111 a and 1111 b) maybe formed to have a single-layer structure using a composite materialcontaining a hole-transport material and an acceptor material(electron-accepting material), or a stacked-layer structure in which alayer including a hole-transport material and a layer including anacceptor material (electron-accepting material) are stacked.

The hole-transport layers (1112 a and 1112 b) transport the holes, whichare injected from the first electrode 1101 by the hole-injection layers(1111 a and 1111 b), to the light-emitting layers (1113 a and 1113 b).Note that the hole-transport layers (1112 a and 1112 b) each contain ahole-transport material. It is particularly preferable that the HOMOlevel of the hole-transport material included in the hole-transportlayers (1112 a and 1112 b) be the same as or close to that of thehole-injection layers (1111 a and 1111 b).

Examples of the acceptor material used for the hole-injection layers(1111 a and 1111 b) include an oxide of a metal belonging to any ofGroups 4 to 8 of the periodic table. Specifically, molybdenum oxide,vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, tungstenoxide, manganese oxide, and rhenium oxide can be given. Among these,molybdenum oxide is especially preferable since it is stable in the air,has a low hygroscopic property, and is easy to handle. Alternatively,organic acceptors such as a quinodimethane derivative, a chloranilderivative, and a hexaazatriphenylene derivative can be used.Specifically, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane(abbreviation: F₄-TCNQ), chloranil,2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation:HAT-CN), and the like can be used.

The hole-transport materials used for the hole-injection layers (1111 aand 1111 b) and the hole-transport layers (1112 a and 1112 b) arepreferably substances with a hole mobility of greater than or equal to10⁻⁶ cm²/Vs. Note that other substances may be used as long as thesubstances have a hole-transport property higher than anelectron-transport property.

Preferred hole-transport materials are π-electron rich heteroaromaticcompounds (e.g., carbazole derivatives and indole derivatives) andaromatic amine compounds, examples of which include compounds having anaromatic amine skeleton, such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD),4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: mBPAFLP),4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBA1BP), 3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole(abbreviation: PCPPn),N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine(abbreviation: PCBiF),N-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine(abbreviation: PCBBiF),4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBBi1BP),4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBANB),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine(abbreviation: PCBAF),N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9′-bifluoren-2-amine(abbreviation: PCBASF), 4,4′,4″-tris(carbazol-9-yl)triphenylamine(abbreviation: TCTA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA), and4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA); compounds having a carbazole skeleton, such as1,3-bis(N-carbazolyl)benzene (abbreviation: mCP),4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP),3,3′-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP),3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene(abbreviation: TCPB), and9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA);compounds having a thiophene skeleton, such as4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation:DBT3P-II),2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene(abbreviation: DBTFLP-III), and4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene(abbreviation: DBTFLP-IV); and compounds having a furan skeleton, suchas 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation:DBF3P-II) and4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran(abbreviation: mmDBFFLBi-II).

A high molecular compound such as poly(N-vinylcarbazole) (abbreviation:PVK), poly(-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:Poly-TPD) can also be used.

Note that the hole-transport material is not limited to the aboveexamples and may be one of or a combination of various known materialswhen used for the hole-injection layers (1111 a and 1111 b) and thehole-transport layers (1112 a and 1112 b).

Next, in the light-emitting element in FIG. 27D, the light-emittinglayer 1113 a is formed over the hole-transport layer 1112 a of the ELlayer 1103 a by a vacuum evaporation method. After the EL layer 1103 aand the charge-generation layer 1104 are formed, the light-emittinglayer 1113 b is formed over the hole-transport layer 1112 b of the ELlayer 1103 b by a vacuum evaporation method.

<<Light-Emitting Layer>>

The light-emitting layers (1113 a and 1113 b) each contain alight-emitting substance. Note that as the light-emitting substance, asubstance whose emission color is blue, violet, bluish violet, green,yellowish green, yellow, orange, red, or the like is appropriately used.When the plurality of light-emitting layers (1113 a and 1113 b) areformed using different light-emitting substances, different emissioncolors can be exhibited (for example, complementary emission colors arecombined to achieve white light emission). Furthermore, a stacked-layerstructure in which one light-emitting layer contains two or more kindsof light-emitting substances may be employed.

The light-emitting layers (1113 a and 1113 b) may each contain one ormore kinds of organic compounds (a host material and an assist material)in addition to a light-emitting substance (guest material). As the oneor more kinds of organic compounds, one or both of the hole-transportmaterial and the electron-transport material described in thisembodiment can be used.

There is no particular limitation on light-emitting substances that canbe used for the light-emitting layers (1113 a and 1113 b), and alight-emitting substance that converts singlet excitation energy intolight emission in the visible light range or a light-emitting substancethat converts triplet excitation energy into light emission in thevisible light range can be used. Examples of the light-emittingsubstance are given below.

As an example of the light-emitting substance that converts singletexcitation energy into light emission, a substance that emitsfluorescence (fluorescent material) can be given. Examples of thesubstance that emits fluorescence include a pyrene derivative, ananthracene derivative, a triphenylene derivative, a fluorene derivative,a carbazole derivative, a dibenzothiophene derivative, a dibenzofuranderivative, a dibenzoquinoxaline derivative, a quinoxaline derivative, apyridine derivative, a pyrimidine derivative, a phenanthrene derivative,and a naphthalene derivative. A pyrene derivative is particularlypreferable because it has a high emission quantum yield. Specificexamples of the pyrene derivative includeN,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPrn),N,N′-diphenyl-N,N′-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6FLPAPrn),N,N′-bis(dibenzofuran-2-yl)-N,N′-diphenylpyrene-1,6-diamine(abbreviation: 1,6FrAPrn),N,N′-bis(dibenzothiophen-2-yl)-N,N′-diphenylpyrene-1,6-diamine(abbreviation: 1,6ThAPrn),N,N′-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-6-amine](abbreviation: 1,6BnfAPrn),N,N′-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-02), andN,N′-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03).

In addition, it is possible to use5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2′-bipyridine (abbreviation:PAP2BPy), 5,6-bis[4′-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2′-bipyridine(abbreviation: PAPP2BPy),N,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA),4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA),4-[4-(10-phenyl-9-anthryl)phenyl]-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPBA), perylene, 2,5,8,11-tetra(tert-butyl)perylene(abbreviation: TBP),N,N′-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N′-triphenyl-1,4-phenylenediamine](abbreviation: DPABPA),N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: 2PCAPPA),N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPPA), or the like.

As examples of a light-emitting substance that converts tripletexcitation energy into light emission, a substance that emitsphosphorescence (phosphorescent material) and a thermally activateddelayed fluorescence (TADF) material that exhibits thermally activateddelayed fluorescence can be given.

Examples of a phosphorescent material include an organometallic complex,a metal complex (platinum complex), and a rare earth metal complex.These substances exhibit the respective emission colors (emission peaks)and thus, any of them is appropriately selected according to need.

As examples of a phosphorescent material which emits blue or green lightand whose emission spectrum has a peak wavelength at greater than orequal to 450 nm and less than or equal to 570 nm, the followingsubstances can be given.

For example, organometallic complexes having a 4H-triazole skeleton,such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III)(abbreviation: [Ir(mpptz-dmp)₃]),tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Mptz)₃]),tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(iPrptz-3b)₃]), andtris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(iPr5btz)₃]); organometallic complexes having a1H-triazole skeleton, such astris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(Mptz1-mp)₃]) andtris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Prptzl-Me)₃]); organometallic complexes having animidazole skeleton, such asfac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III)(abbreviation: [Ir(iPrpmi)₃]) andtris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III)(abbreviation: [Ir(dmpimpt-Me)₃]); organometallic complexes in which aphenylpyridine derivative having an electron-withdrawing group is aligand, such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: FIr6),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III) picolinate(abbreviation: FIrpic),bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C^(2′)}iridium(III)picolinate (abbreviation: [Ir(CF₃ppy)₂(pic)]), andbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)acetylacetonate (abbreviation: FIr(acac)); and the like can be given.

As examples of a phosphorescent material which emits green or yellowlight and whose emission spectrum has a peak wavelength at greater thanor equal to 495 nm and less than or equal to 590 nm, the followingsubstances can be given.

For example, organometallic iridium complexes having a pyrimidineskeleton, such as tris(4-methyl-6-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₃]),tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation:[Ir(tBuppm)₃]),(acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₂(acac)]),(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]),(acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(nbppm)₂(acac)]),(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(mpmppm)₂(acac)]),(acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}iridium(III)(abbreviation: [Ir(dmppm-dmp)₂(acac)]), and(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: [Ir(dppm)₂(acac)]); organometallic iridium complexeshaving a pyrazine skeleton, such as(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-Me)₂(acac)]) and(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-iPr)₂(acac)]); organometallic iridium complexeshaving a pyridine skeleton, such astris(2-phenylpyridinato-N,C^(2′))iridium(III) (abbreviation:[Ir(ppy)₃]), bis(2-phenylpyridinato-N,C^(2′))iridium(III)acetylacetonate (abbreviation: [Ir(ppy)₂(acac)]),bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation:[Ir(bzq)₂(acac)]), tris(benzo[h]quinolinato)iridium(III) (abbreviation:[Ir(bzq)₃]), tris(2-phenylquinolinato-N,C^(2′))iridium(III)(abbreviation: [Ir(pq)₃]), andbis(2-phenylquinolinato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(pq)₂(acac)]); organometallic complexes such asbis(2,4-diphenyl-1,3-oxazolato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(dpo)₂(acac)]),bis{2-[4′-(perfluorophenyl)phenyl]pyridinato-N,C^(2′)}iridium(III)acetylacetonate (abbreviation: [Ir(p-PF-ph)₂(acac)]), andbis(2-phenylbenzothiazolato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(bt)₂(acac)]); and rare earth metal complexes such astris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation:[Tb(acac)₃(Phen)]) can be given.

As examples of a phosphorescent material which emits yellow or red lightand whose emission spectrum has a peak wavelength at greater than orequal to 570 nm and less than or equal to 750 nm, the followingsubstances can be given.

For example, organometallic complexes having a pyrimidine skeleton, suchas(diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III)(abbreviation: [Ir(5mdppm)₂(dibm)]),bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: [Ir(5mdppm)₂(dpm)]), andbis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(d1npm)₂(dpm)]);organometallic complexes having a pyrazine skeleton, such as(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]),bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III)(abbreviation: [Ir(tppr)₂(dpm)]),bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-P)₂(dibm)]),bis{4,6-dimethyl-2-[5-(4-cyano-2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-dmCP)₂(dpm)]),(acetylacetonato)bis[2-methyl-3-phenylquinoxalinato-N,C^(2′)]iridium(III)(abbreviation: [Ir(mpq)₂(acac)]),(acetylacetonato)bis(2,3-diphenylquinoxalinato-N,C^(2′))iridium(III)(abbreviation: [Ir(dpq)₂(acac)]), and(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: [Ir(Fdpq)₂(acac)]); organometallic complexes having apyridine skeleton, such astris(1-phenylisoquinolinato-N,C^(2′))iridium(III) (abbreviation:[Ir(piq)₃]) and bis(1-phenylisoquinolinato-N,C^(2′))iridium(III)acetylacetonate (abbreviation: [Ir(piq)₂(acac)]); platinum complexessuch as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II)(abbreviation: [PtOEP]); and rare earth metal complexes such astris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III)(abbreviation: [Eu(DBM)₃(Phen)]) andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: [Eu(TTA)₃(Phen)]) can be given.

As the organic compounds (the host material and the assist material)used in the light-emitting layers (1113 a and 1113 b), one or more kindsof substances having a larger energy gap than the light-emittingsubstance (the guest material) are used.

When the light-emitting substance is a fluorescent material, it ispreferable to use an organic compound that has a high energy level in asinglet excited state and has a low energy level in a triplet excitedstate. For example, an anthracene derivative or a tetracene derivativeis preferably used. Specific examples include9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation:PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation:CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA),6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan(abbreviation: 2mBnfPPA),9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl}anthracene(abbreviation: FLPPA), 5,12-diphenyltetracene, and5,12-bis(biphenyl-2-yl)tetracene.

In the case where the light-emitting substance is a phosphorescentmaterial, an organic compound having triplet excitation energy (energydifference between a ground state and a triplet excited state) which ishigher than that of the light-emitting substance is preferably selected.In that case, it is possible to use a zinc- or aluminum-based metalcomplex, an oxadiazole derivative, a triazole derivative, abenzimidazole derivative, a quinoxaline derivative, a dibenzoquinoxalinederivative, a dibenzothiophene derivative, a dibenzofuran derivative, apyrimidine derivative, a triazine derivative, a pyridine derivative, abipyridine derivative, a phenanthroline derivative, an aromatic amine, acarbazole derivative, and the like.

Specific examples include metal complexes such astris(8-quinolinolato)aluminum(III) (abbreviation: Alq),tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq),bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), andbis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ);heterocyclic compounds such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP),2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation:NBphen), and 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole(abbreviation: CO11); and aromatic amine compounds such as NPB, TPD, andBSPB.

In addition, condensed polycyclic aromatic compounds such as anthracenederivatives, phenanthrene derivatives, pyrene derivatives, chrysenederivatives, and dibenzo[g,p]chrysene derivatives can be used.Specifically, 9,10-diphenylanthracene (abbreviation: DPAnth),N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine(abbreviation: DPhPA), YGAPA, PCAPA,N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine(abbreviation: PCAPBA), 2PCAPA, 6,12-dimethoxy-5,11-diphenylchrysene,DBC1, 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation:CzPA), 3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: DPCzPA), 9,10-bis(3,5-diphenylphenyl)anthracene(abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA),2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),9,9′-bianthryl (abbreviation: BANT),9,9′-(stilbene-3,3′-diyl)diphenanthrene (abbreviation: DPNS),9,9′-(stilbene-4,4′-diyl)diphenanthrene (abbreviation: DPNS2),1,3,5-tri(1-pyrenyl)benzene (abbreviation: TPB3), or the like can beused.

In the case where a plurality of organic compounds are used for thelight-emitting layers (1113 a and 1113 b), it is preferable to usecompounds that form an exciplex in combination with each other. In thatcase, although any of various organic compounds can be used in anappropriate combination, in order to form an exciplex efficiently, it isparticularly preferable to combine a compound that easily accepts holes(hole-transport material) and a compound that easily accepts electrons(electron-transport material). As the hole-transport material and theelectron-transport material, specifically, any of the materialsdescribed in this embodiment can be used.

The TADF material is a material that can up-convert a triplet excitedstate into a singlet excited state (i.e., reverse intersystem crossingis possible) using a little thermal energy and efficiently exhibitslight emission (fluorescence) from the singlet excited state. The TADFis efficiently obtained under the condition where the difference inenergy between the triplet excited level and the singlet excited levelis greater than or equal to 0 eV and less than or equal to 0.2 eV,preferably greater than or equal to 0 eV and less than or equal to 0.1eV. Note that “delayed fluorescence” exhibited by the TADF materialrefers to light emission having the same spectrum as normal fluorescenceand an extremely long lifetime. The lifetime is 10⁻⁶ seconds or longer,preferably 10⁻³ seconds or longer.

Examples of the TADF material include fullerene, a derivative thereof,an acridine derivative such as proflavine, and eosin. Other examplesinclude a metal-containing porphyrin, such as a porphyrin containingmagnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium(In), or palladium (Pd). Examples of the metal-containing porphyrininclude a protoporphyrin-tin fluoride complex (abbreviation: SnF₂(ProtoIX)), a mesoporphyrin-tin fluoride complex (abbreviation: SnF₂(MesoIX)), a hematoporphyrin-tin fluoride complex (abbreviation: SnF₂(HematoIX)), a coproporphyrin tetramethyl ester-tin fluoride complex(abbreviation: SnF₂(Copro III-4Me)), an octaethylporphyrin-tin fluoridecomplex (abbreviation: SnF₂(OEP)), an etioporphyrin-tin fluoride complex(abbreviation: SnF₂(Etio I)), and an octaethylporphyrin-platinumchloride complex (abbreviation: PtCl₂OEP).

Alternatively, a heterocyclic compound having a π-electron richheteroaromatic ring and a π-electron deficient heteroaromatic ring, suchas2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine(abbreviation: PIC-TRZ),2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine(abbreviation: PCCzPTzn),2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine(abbreviation: PXZ-TRZ),3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole(abbreviation: PPZ-3TPT),3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation:ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone(abbreviation: DMAC-DPS), or10-phenyl-10H,10′H-spiro[acridin-9,9′-anthracen]-10′-one (abbreviation:ACRSA) can be used. Note that a substance in which the π-electron richheteroaromatic ring is directly bonded to the π-electron deficientheteroaromatic ring is particularly preferable because both the donorproperty of the π-electron rich heteroaromatic ring and the acceptorproperty of the π-electron deficient heteroaromatic ring are increasedand the energy difference between the singlet excited state and thetriplet excited state becomes small.

Note that when a TADF material is used, the TADF material can becombined with another organic compound.

Then, in the light-emitting element in FIG. 27D, an electron-transportlayer 1114 a is formed over the light-emitting layer 1113 a of the ELlayer 1103 a by a vacuum evaporation method. After the EL layer 1103 aand the charge-generation layer 1104 are formed, an electron-transportlayer 1114 b is formed over the light-emitting layer 1113 b of the ELlayer 1103 b by a vacuum evaporation method.

<<Electron-Transport Layer>>

The electron-transport layers (1114 a and 1114 b) transport theelectrons, which are injected from the second electrode 1102 by theelectron-injection layers (1115 a and 1115 b), to the light-emittinglayers (1113 a and 1113 b). Note that the electron-transport layers(1114 a and 1114 b) each contain an electron-transport material. It ispreferable that the electron-transport materials included in theelectron-transport layers (1114 a and 1114 b) be substances with anelectron mobility of higher than or equal to 1×10⁻⁶ cm²/Vs. Note thatother substances may also be used as long as the substances have anelectron-transport property higher than a hole-transport property.

Examples of the electron-transport material include metal complexeshaving a quinoline ligand, a benzoquinoline ligand, an oxazole ligand,and a thiazole ligand; an oxadiazole derivative; a triazole derivative;a phenanthroline derivative; a pyridine derivative; and a bipyridinederivative. In addition, a π-electron deficient heteroaromatic compoundsuch as a nitrogen-containing heteroaromatic compound can also be used.

Specifically, it is possible to use metal complexes such as Alq₃,tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq₂), BAlq,bis[2-(2-hydroxyphenyl)benzoxazolato]zinc(II) (abbreviation: Zn(BOX)₂),and bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation:Zn(BTZ)₂), heteroaromatic compounds such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), OXD-7,3-(4′-tert-butylphenyl)-4-phenyl-5-(4″-biphenyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP), and4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs), andquinoxaline derivatives and dibenzoquinoxaline derivatives such as2[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline(abbreviation: 2CzPDB q-III),7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:7mDBTPDBq-II), and6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:6mDBTPDB q-II).

Alternatively, a high molecular compound such as poly(2,5-pyridinediyl)(abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py), orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) can be used.

Each of the electron-transport layers (1114 a and 1114 b) is not limitedto a single layer, but may be a stack of two or more layers eachcontaining any of the above substances.

Next, in the light-emitting element in FIG. 27D, the electron-injectionlayer 1115 a is formed over the electron-transport layer 1114 a of theEL layer 1103 a by a vacuum evaporation method. Subsequently, the ELlayer 1103 a and the charge-generation layer 1104 are formed, thecomponents up to the electron-transport layer 1114 b of the EL layer1103 b are formed, and then the electron-injection layer 1115 b isformed thereover by a vacuum evaporation method.

<<Electron-Injection Layer>>

The electron-injection layers (1115 a and 1115 b) each contain asubstance having a high electron-injection property. Theelectron-injection layers (1115 a and 1115 b) can each be formed usingan alkali metal, an alkaline earth metal, or a compound thereof, such aslithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF₂),or lithium oxide (LiO_(x)). A rare earth metal compound like erbiumfluoride (ErF₃) can also be used. Electride may also be used for theelectron-injection layers (1115 a and 1115 b). Examples of the electrideinclude a substance in which electrons are added at high concentrationto calcium oxide-aluminum oxide. Any of the substances for forming theelectron-transport layers (1114 a and 1114 b), which are given above,can also be used.

A composite material in which an organic compound and an electron donor(donor) are mixed may also be used for the electron-injection layers(1115 a and 1115 b). Such a composite material is excellent in anelectron-injection property and an electron-transport property becauseelectrons are generated in the organic compound by the electron donor.The organic compound here is preferably a material excellent intransporting the generated electrons; specifically, for example, theelectron-transport materials for forming the electron-transport layers(1114 a and 1114 b) (e.g., a metal complex or a heteroaromatic compound)can be used. As the electron donor, a substance showing anelectron-donating property with respect to the organic compound may beused. Preferable examples are an alkali metal, an alkaline earth metal,and a rare earth metal. Specifically, lithium, cesium, magnesium,calcium, erbium, ytterbium, and the like can be given. Furthermore, analkali metal oxide and an alkaline earth metal oxide are preferable, anda lithium oxide, a calcium oxide, a barium oxide, and the like can begiven. Alternatively, a Lewis base such as magnesium oxide can be used.Further alternatively, an organic compound such as tetrathiafulvalene(abbreviation: TTF) can be used.

In the case where light obtained from the light-emitting layer 1113 b isamplified, for example, the optical path length between the secondelectrode 1102 and the light-emitting layer 1113 b is preferably lessthan one fourth of the wavelength λ of light emitted from thelight-emitting layer 1113 b. In that case, the optical path length canbe adjusted by changing the thickness of the electron-transport layer1114 b or the electron-injection layer 1115 b.

<<Charge-Generation Layer>>

The charge-generation layer 1104 has a function of injecting electronsinto the EL layer 1103 a and injecting holes into the EL layer 1103 bwhen voltage is applied between the first electrode (anode) 1101 and thesecond electrode (cathode) 1102. The charge-generation layer 1104 mayhave either a structure in which an electron acceptor (acceptor) isadded to a hole-transport material or a structure in which an electrondonor (donor) is added to an electron-transport material. Alternatively,both of these structures may be stacked. Note that forming thecharge-generation layer 1104 by using any of the above materials cansuppress an increase in drive voltage caused by the stack of the ELlayers.

In the case where the charge-generation layer 1104 has a structure inwhich an electron acceptor is added to a hole-transport material, any ofthe materials described in this embodiment can be used as thehole-transport material. As the electron acceptor, it is possible to use7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ), chloranil, and the like. In addition, oxides of metals thatbelong to Group 4 to Group 8 of the periodic table can be given.Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromiumoxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide,or the like is used.

In the case where the charge-generation layer 1104 has a structure inwhich an electron donor is added to an electron-transport material, anyof the materials described in this embodiment can be used as theelectron-transport material. As the electron donor, it is possible touse an alkali metal, an alkaline earth metal, a rare earth metal, metalsthat belong to Groups 2 and 13 of the periodic table, or an oxide orcarbonate thereof. Specifically, lithium (Li), cesium (Cs), magnesium(Mg), calcium (Ca), ytterbium (Yb), indium (In), lithium oxide, cesiumcarbonate, or the like is preferably used. Alternatively, an organiccompound such as tetrathianaphthacene may be used as the electron donor.

<<Substrate>>

The light-emitting element described in this embodiment can be formedover any of a variety of substrates. Note that the type of the substrateis not limited to a certain type. Examples of the substrate include asemiconductor substrate (e.g., a single crystal substrate or a siliconsubstrate), an SOI substrate, a glass substrate, a quartz substrate, aplastic substrate, a metal substrate, a stainless steel substrate, asubstrate including stainless steel foil, a tungsten substrate, asubstrate including tungsten foil, a flexible substrate, an attachmentfilm, paper including a fibrous material, and a base material film.

Examples of the glass substrate include a barium borosilicate glasssubstrate, an aluminoborosilicate glass substrate, and a soda lime glasssubstrate. Examples of the flexible substrate, the attachment film, andthe base material film include plastics typified by polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), and polyethersulfone (PES); a synthetic resin such as acrylic; polypropylene;polyester; polyvinyl fluoride; polyvinyl chloride; polyamide; polyimide;aramid; epoxy; an inorganic vapor deposition film; and paper.

For fabrication of the light-emitting element in this embodiment, avacuum process such as an evaporation method or a solution process suchas a spin coating method or an ink-jet method can be used. When anevaporation method is used, a physical vapor deposition method (PVDmethod) such as a sputtering method, an ion plating method, an ion beamevaporation method, a molecular beam evaporation method, or a vacuumevaporation method, a chemical vapor deposition method (CVD method), orthe like can be used. Specifically, the functional layers (thehole-injection layers (1111 a and 1111 b), the hole-transport layers(1112 a and 1112 b), the light-emitting layers (1113 a and 1113 b), theelectron-transport layers (1114 a and 1114 b), the electron-injectionlayers (1115 a and 1115 b)) included in the EL layers and thecharge-generation layer 1104 of the light-emitting element can be formedby an evaporation method (e.g., a vacuum evaporation method), a coatingmethod (e.g., a dip coating method, a die coating method, a bar coatingmethod, a spin coating method, or a spray coating method), a printingmethod (e.g., an ink-jet method, screen printing (stencil), offsetprinting (planography), flexography (relief printing), gravure printing,or micro-contact printing), or the like.

Note that materials that can be used for the functional layers (thehole-injection layers (1111 a and 1111 b), the hole-transport layers(1112 a and 1112 b), the light-emitting layers (1113 a and 1113 b), theelectron-transport layers (1114 a and 1114 b), and theelectron-injection layers (1115 a and 1115 b)) that are included in theEL layers (1103 a and 1103 b) and the charge-generation layer 1104 inthe light-emitting element described in this embodiment are not limitedto the above materials, and other materials can be used in combinationas long as the functions of the layers are fulfilled. For example, ahigh molecular compound (e.g., an oligomer, a dendrimer, or a polymer),a middle molecular compound (a compound between a low molecular compoundand a high molecular compound with a molecular weight of 400 to 4000),an inorganic compound (e.g., a quantum dot material), or the like can beused. The quantum dot may be a colloidal quantum dot, an alloyed quantumdot, a core-shell quantum dot, a core quantum dot, or the like.

The structure described in this embodiment can be combined asappropriate with any of the structures described in the otherembodiments or the example in this specification.

Embodiment 6

In this embodiment, a light-emitting device of one embodiment of thepresent invention is described. Note that a light-emitting deviceillustrated in FIG. 28A is an active-matrix light-emitting device inwhich transistors (FETs) 1202 are electrically connected tolight-emitting elements (1203R, 1203G, 1203B, and 1203W) over a firstsubstrate 1201. The light-emitting elements (1203R, 1203G, 1203B, and1203W) include a common EL layer 1204 and each have a microcavitystructure in which the optical path length between electrodes isadjusted depending on the emission color of the light-emitting element.The light-emitting device is a top-emission light-emitting device inwhich light is emitted from the EL layer 1204 through color filters(1206R, 1206G, and 1206B) formed on a second substrate 1205.

The light-emitting device illustrated in FIG. 28A is fabricated suchthat a first electrode 1207 functions as a reflective electrode and asecond electrode 1208 functions as a transflective electrode. Note thatdescription in any of the other embodiments can be referred to asappropriate for electrode materials for the first electrode 1207 and thesecond electrode 1208.

In the case where the light-emitting element 1203R functions as a redlight-emitting element, the light-emitting element 1203G functions as agreen light-emitting element, the light-emitting element 1203B functionsas a blue light-emitting element, and the light-emitting element 1203Wfunctions as a white light-emitting element in FIG. 28A, for example, agap between the first electrode 1207 and the second electrode 1208 inthe light-emitting element 1203R is adjusted to have an optical pathlength 1211R, a gap between the first electrode 1207 and the secondelectrode 1208 in the light-emitting element 1203G is adjusted to havean optical path length 1211G, and a gap between the first electrode 1207and the second electrode 1208 in the light-emitting element 1203B isadjusted to have an optical path length 1211B as illustrated in FIG.28B. Note that optical adjustment can be performed in such a manner thata conductive layer 1210R is stacked over the first electrode 1207 in thelight-emitting element 1203R and a conductive layer 1210G is stackedover the first electrode 1207 in the light-emitting element 1203G asillustrated in FIG. 28B.

The second substrate 1205 is provided with the color filters (1206R,1206G, and 1206B). Note that the color filters each transmit visiblelight in a specific wavelength range and blocks visible light in theother wavelength ranges. Thus, as illustrated in FIG. 28A, the colorfilter 1206R that transmits only light in the red wavelength range isprovided in a position overlapping with the light-emitting element1203R, whereby red light emission can be obtained from thelight-emitting element 1203R. Furthermore, the color filter 1206G thattransmits only light in the green wavelength range is provided in aposition overlapping with the light-emitting element 1203G, wherebygreen light emission can be obtained from the light-emitting element1203G. Moreover, the color filter 1206B that transmits only light in theblue wavelength range is provided in a position overlapping with thelight-emitting element 1203B, whereby blue light emission can beobtained from the light-emitting element 1203B. Note that thelight-emitting element 1203W can emit white light without a colorfilter. Note that a black layer (black matrix) 1209 may be provided atan end portion of each color filter. The color filters (1206R, 1206G,and 1206B) and the black layer 1209 may be covered with an overcoatlayer formed using a transparent material.

Although the light-emitting device in FIG. 28A has a structure in whichlight is extracted from the second substrate 1205 side (top emissionstructure), a structure in which light is extracted from the firstsubstrate 1201 side where the FETs 1202 are formed (bottom emissionstructure) may be employed as illustrated in FIG. 28C. In the case of abottom-emission light-emitting device, the first electrode 1207 isformed as a transflective electrode and the second electrode 1208 isformed as a reflective electrode. As the first substrate 1201, asubstrate having at least a light-transmitting property is used. Asillustrated in FIG. 28C, color filters (1206R′, 1206G′, and 1206B) areprovided so as to be closer to the first substrate 1201 than thelight-emitting elements (1203R, 1203G, and 1203B) are.

In FIG. 28A, the light-emitting elements are the red light-emittingelement, the green light-emitting element, the blue light-emittingelement, and the white light-emitting element; however, thelight-emitting elements that can be used in the display device of oneembodiment of the present invention are not limited to the above, and ayellow light-emitting element or an orange light-emitting element may beused. Note that description in any of the other embodiments can bereferred to as appropriate for materials that are used for the EL layers(a light-emitting layer, a hole-injection layer, a hole-transport layer,an electron-transport layer, an electron-injection layer, acharge-generation layer, and the like) to fabricate each of thelight-emitting elements. In that case, a color filter needs to beappropriately selected depending on the emission color of thelight-emitting element.

With the above structure, a light-emitting device includinglight-emitting elements that exhibit a plurality of emission colors canbe fabricated.

This embodiment can be implemented in an appropriate combination withany of the other embodiments and an example in this specification.

Example 1

In this example, a sample including a glass substrate over an elasticsupport substrate is described.

FIG. 29 schematically illustrates a sample in which substrates 503 areprovided over a support substrate 501 at intervals MMT. Note that thesupport substrate 501 and each of the substrates 503 correspond to thesupport substrate 301 and the display unit 250 b in the manufacturingmethod example in Embodiment 3 described with reference to FIG. 20B,respectively.

Adhesives 502 are positioned in regions where the substrates 503 overlapwith the support substrate 501. The adhesives 502 are used for bondingthe substrates 503 onto the support substrate 501.

FIG. 30A is a photograph of a sample in which a silicone rubber sheet(KS05000, produced by Kyowa Industries, Inc.) was used as the supportsubstrate 501, Super X No. 8008 (produced by CEMEDINE Co., Ltd.) wasused as each of the adhesives 502, and glass substrates (AN100, producedby Asahi Glass Co., Ltd.) were used as the substrates 503. Thesubstrates 503 were each processed into 10 mm square and provided in amatrix of four rows and three columns over the support substrate 501with an interval MMT of 10 mm.

FIG. 30B is an image of the sample in FIG. 30A stretched in the sdirection. FIG. 30C is an image of the sample in FIG. 30A stretched inthe t direction. FIG. 30D is an image of the sample in FIG. 30Astretched in the u direction. Note that FIGS. 30B to 30D each show thesample stretched by 10 mm or more and 20 mm or less with the hands of anexperimenter.

The sample in FIG. 30A formed using the above-described materials can bestretched without the separation of the substrates 503 from the supportsubstrate 501 as shown in FIGS. 30B to 30D.

Note that the structures described in this example can be used incombination with any of the structures described in the otherembodiments as appropriate.

REFERENCE NUMERALS

SLa[1]: signal line, SLa[2]: signal line, SLb[1]: signal line, SLb[2]:signal line, SL[1]: signal line, SL[2]: signal line, GLa[1]: gate line,GLa[2]: gate line, GLb[1]: gate line, GLb[2]: gate line, 30: unit, 31:unit, 32: connection region, 41: conductor, 41 a: disk, 41 b: column, 41c: disk, 42: conductor, 43: conductor, 44: conductor, 44 a: disk, 44 b:cylinder, 44 c: disk, 45: conductor, 46: conductor, 47: conductor, 48:conductor, 51: code, 52: code, 53: code, 54: code, 60: shaft, 60A:shaft, 60 a: shaft, 60 b: shaft, 60 c: shaft, 60 d: shaft, 60 e: shaft,60 f: shaft, 60 g: shaft, 60 h: shaft, 60 i: shaft, 61: shaft, 62:shaft, 69 b[1]: opening, 69 b[2]: opening, 69 c[1]: opening, 69 c[2]:opening, 70: support unit, 72: connection region, 73: support, 80:display unit, 80A: display unit, 80B: display unit, 80 a: display unit,80 b: display unit, 80 c: display unit, 80 d: display unit, 81: displayportion, 81A: display portion, 82: connection region, 82 a: connectionregion, 82 b: connection region, 82 c: connection region, 82 d:connection region, 82 e: connection region, 82 f: connection region, 82g: connection region, 82 h: connection region, 83: support, 83A:support, 85: display unit group, 85A: display unit group, 85B: displayunit group, 85C: display unit group, 86: display unit group, 86A:display unit group, 86B: display unit group, 80[1]: display unit, 80[2]:display unit, 80[3]: display unit, 80[4]: display unit, 86 b: wiring, 86c: wiring, 90: driver circuit unit, 91: driver circuit portion, 92:connection region, 93: support, 100: display device, 100 a: region, 100b: region, 100A: display device, 100B: display device, 101: displayregion, 101 a: region, 101 b: region, 102A: driver region, 102B: driverregion, 105 a: region, 105 b: region, 106: region, 240: insulator, 250:display unit, 250 a: display unit, 250 a[1]: display unit, 250 a[2]:display unit, 250 b: display unit, 251: circuit, 252: light-emittingportion, 255: display unit, 256: circuit, 260: display region, 260A:display region, 260B: display region, 261A: display region, 261B:display region, 262A: display region, 262B: display region, 270: driverregion, 270A: driver region, 271: driver circuit unit, 272: wiring, 280:driver region, 280A: driver region, 281: driver circuit unit, 282:wiring, 301: support substrate, 302: substrate, 303: substrate, 311:substrate, 315: substrate, 321: insulator, 322: insulator, 323:insulator, 324: insulator, 325: insulator, 326: insulator, 341:conductor, 342 a: conductor, 342 b: conductor, 343: conductor, 344 a:conductor, 344 b: conductor, 345: conductor, 350: metal oxide, 361:opening, 362: opening, 370: light-emitting element, 380: conductor, 381:conductor, 390: protective layer, 391: protective layer, 401:transistor, 501: support substrate, 502: adhesive, 503: substrate, 1101:electrode, 1102: electrode, 1103: EL layer, 1103 a: EL layer, 1103 b: ELlayer, 1104: charge-generation layer, 1111: hole-injection layer, 1111a: hole-injection layer, 1111 b: hole-injection layer, 1112:hole-transport layer, 1112 a: hole-transport layer, 1112 b:hole-transport layer, 1113: light-emitting layer, 1113 a: light-emittinglayer, 1113 b: light-emitting layer, 1114: electron-transport layer,1114 a: electron-transport layer, 1114 b: electron-transport layer,1115: electron-injection layer, 1115 a: electron-injection layer, 1115b: electron-injection layer, 1201: substrate, 1202: FET, 1203R:light-emitting element, 1203G: light-emitting element, 1203B:light-emitting element, 1203W: light-emitting element, 1204: EL layer,1205: substrate, 1206R: color filter, 1206R′: color filter, 1206G: colorfilter, 1206G′: color filter, 1206B: color filter, 1206B′: color filter,1207: electrode, 1208: electrode, 1209: black layer, 1210R: conductivelayer, 1210G: conductive layer, 1211R: optical path length, 1211G:optical path length, 1211B: optical path length, 5701: display panel,5702: display panel, 5703: display panel, 5704: display panel, 5801:clothing, 5802: display portion, 5901: housing, 5902: display portion,5903: operation button, 5904: operator, 5905: band, 6001: building,6002: signboard, 6002A: signboard, 6003: steel frame, 6100: digitalsignage, 6101: display portion, 6102: structure body, 6103: caster,6200A: digital signage, 6200B: digital signage, 6201: wall, 6300A:digital signage, 6300B: digital signage 6301: wall, 7000: electronicdevice, and 7001: finger.

This application is based on Japanese Patent Application Serial No.2016-248914 filed with Japan Patent Office on Dec. 22, 2016 and JapanesePatent Application Serial No. 2017-159979 filed with Japan Patent Officeon Aug. 23, 2017, the entire contents of which are hereby incorporatedby reference.

The invention claimed is:
 1. A display device comprising: a displayregion comprising: a first layer comprising a plurality of first units;and a second layer comprising a plurality of second units and a firstinsulator, wherein the second layer is placed over the first layer, andwherein the first insulator comprises a light-transmitting and elasticmaterial, wherein each of the plurality of first units is smaller thaneach of the plurality of second units in size, wherein the plurality offirst units each comprise a first light-emitting portion, wherein theplurality of second units each comprise a second light-emitting portion,wherein a first one of the plurality of first units comprises a firstregion overlapping with two of the second units that are adjacent toeach other, wherein a second one of the plurality of first unitscomprises a second region overlapping with four of the second units thatare arranged in adjacent two rows and two columns, wherein an area ofeach of the first region and the second region is configured to bechanged by stretching the first insulator, wherein when the firstinsulator is stretched, a whole of the first light-emitting portion ofthe first one of the plurality of first units is exposed between the twoof the second units that are adjacent to each other, wherein when thefirst insulator is stretched, a whole of the first light-emittingportion of the second one of the plurality of first units is exposedbetween the four of the second units that are arranged in adjacent tworows and two columns, and wherein an aspect ratio of the display deviceis changeable.
 2. The display device according to claim 1, furthercomprising a driver region comprising a plurality of third units and aplurality of fourth units, wherein the plurality of third units areconfigured to drive the first light-emitting portions of the pluralityof first units, wherein the plurality of fourth units are configured todrive the second light-emitting portions of the plurality of secondunits, and wherein the plurality of fourth units are placed over theplurality of third units.
 3. The display device according to claim 1,wherein the first layer of the display region further comprises a secondinsulator.
 4. The display device according to claim 1, wherein the firstlight-emitting portions each comprise a light-emitting element, andwherein the second light-emitting portions each comprise alight-emitting element.